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	$38.65	7.482%	$41.5418	$41.54	$41.55	$41.50
Purchase #2	$133.83	10.831%	$148.3251	$148.33	$148.35	$148.30
Purchase #3	$133.41	11.150%	$148.2852	$148.29	$148.30	$148.30
Purchase #4	$104.80	6.194%	$111.2913	$111.29	$111.30	$111.30
Purchase #5	$93.79	5.494%	$98.9428	$98.94	$98.95	$98.90
Purchase #6	$148.26	12.322%	$166.5286	$166.53	$166.55	$166.50
Purchase #7	$32.78	10.415%	$36.194	$36.19	$36.20	$36.20
7 purchase totals =	$685.52		$751.1088	$751.11	$751.20	$751.00