Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.34	13.339%	$103.5238	$103.52	$103.50	$103.50
Purchase #2	$202.97	5.253%	$213.632	$213.63	$213.65	$213.60
Purchase #3	$182.48	7.790%	$196.6952	$196.70	$196.70	$196.70
Purchase #4	$98.48	11.155%	$109.4654	$109.47	$109.45	$109.50
Purchase #5	$133.43	13.311%	$151.1909	$151.19	$151.20	$151.20
Purchase #6	$120.79	3.794%	$125.3728	$125.37	$125.35	$125.40
Purchase #7	$174.70	13.526%	$198.3299	$198.33	$198.35	$198.30
7 purchase totals =	$1,004.19		$1,098.2100	$1,098.21	$1,098.20	$1,098.20