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	$51.79	9.541%	$56.7313	$56.73	$56.75	$56.70
Purchase #2	$63.97	13.840%	$72.8234	$72.82	$72.80	$72.80
Purchase #3	$73.67	6.138%	$78.1919	$78.19	$78.20	$78.20
Purchase #4	$182.34	8.804%	$198.3932	$198.39	$198.40	$198.40
Purchase #5	$110.80	7.692%	$119.3227	$119.32	$119.30	$119.30
Purchase #6	$46.46	8.300%	$50.3162	$50.32	$50.30	$50.30
Purchase #7	$16.67	10.744%	$18.461	$18.46	$18.45	$18.50
7 purchase totals =	$545.70		$594.2397	$594.23	$594.20	$594.20