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	$58.53	7.477%	$62.9063	$62.91	$62.90	$62.90
Purchase #2	$206.25	3.472%	$213.411	$213.41	$213.40	$213.40
Purchase #3	$113.98	10.657%	$126.1268	$126.13	$126.15	$126.10
Purchase #4	$209.38	6.605%	$223.2095	$223.21	$223.20	$223.20
Purchase #5	$71.32	9.764%	$78.2837	$78.28	$78.30	$78.30
Purchase #6	$61.86	4.221%	$64.4711	$64.47	$64.45	$64.50
Purchase #7	$245.31	12.319%	$275.5297	$275.53	$275.55	$275.50
7 purchase totals =	$966.63		$1,043.9381	$1,043.94	$1,043.95	$1,043.90