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	$213.40	7.108%	$228.5685	$228.57	$228.55	$228.60
Purchase #2	$15.56	12.323%	$17.4775	$17.48	$17.50	$17.50
Purchase #3	$190.72	3.238%	$196.8955	$196.90	$196.90	$196.90
Purchase #4	$175.81	9.147%	$191.8913	$191.89	$191.90	$191.90
Purchase #5	$55.93	4.228%	$58.2947	$58.29	$58.30	$58.30
Purchase #6	$128.65	11.327%	$143.2222	$143.22	$143.20	$143.20
Purchase #7	$223.58	9.173%	$244.089	$244.09	$244.10	$244.10
7 purchase totals =	$1,003.65		$1,080.4387	$1,080.44	$1,080.45	$1,080.50