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	$189.88	12.477%	$213.5713	$213.57	$213.55	$213.60
Purchase #2	$240.95	5.784%	$254.8865	$254.89	$254.90	$254.90
Purchase #3	$186.48	5.154%	$196.0912	$196.09	$196.10	$196.10
Purchase #4	$147.56	8.808%	$160.5571	$160.56	$160.55	$160.60
Purchase #5	$235.48	10.121%	$259.3129	$259.31	$259.30	$259.30
Purchase #6	$229.51	10.456%	$253.5076	$253.51	$253.50	$253.50
Purchase #7	$211.59	5.345%	$222.8995	$222.90	$222.90	$222.90
7 purchase totals =	$1,441.45		$1,560.8261	$1,560.83	$1,560.80	$1,560.90