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	$140.27	11.570%	$156.4992	$156.50	$156.50	$156.50
Purchase #2	$131.36	4.830%	$137.7047	$137.70	$137.70	$137.70
Purchase #3	$168.32	6.744%	$179.6715	$179.67	$179.65	$179.70
Purchase #4	$81.54	11.481%	$90.9016	$90.90	$90.90	$90.90
Purchase #5	$44.27	4.681%	$46.3423	$46.34	$46.35	$46.30
Purchase #6	$236.58	12.435%	$265.9987	$266.00	$266.00	$266.00
Purchase #7	$162.56	7.369%	$174.539	$174.54	$174.55	$174.50
7 purchase totals =	$964.90		$1,051.6570	$1,051.65	$1,051.65	$1,051.60