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	$41.44	9.298%	$45.2931	$45.29	$45.30	$45.30
Purchase #2	$222.58	5.485%	$234.7885	$234.79	$234.80	$234.80
Purchase #3	$248.34	6.567%	$264.6485	$264.65	$264.65	$264.60
Purchase #4	$221.37	3.700%	$229.5607	$229.56	$229.55	$229.60
Purchase #5	$181.33	5.386%	$191.0964	$191.10	$191.10	$191.10
Purchase #6	$93.46	7.664%	$100.6228	$100.62	$100.60	$100.60
Purchase #7	$205.91	10.301%	$227.1208	$227.12	$227.10	$227.10
7 purchase totals =	$1,214.43		$1,293.1308	$1,293.13	$1,293.10	$1,293.10