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	$249.89	10.511%	$276.1559	$276.16	$276.15	$276.20
Purchase #2	$166.49	4.652%	$174.2351	$174.24	$174.25	$174.20
Purchase #3	$180.33	5.425%	$190.1129	$190.11	$190.10	$190.10
Purchase #4	$37.79	9.769%	$41.4817	$41.48	$41.50	$41.50
Purchase #5	$52.29	13.704%	$59.4558	$59.46	$59.45	$59.50
Purchase #6	$96.35	3.577%	$99.7964	$99.80	$99.80	$99.80
Purchase #7	$66.86	6.548%	$71.238	$71.24	$71.25	$71.20
7 purchase totals =	$850.00		$912.4758	$912.49	$912.50	$912.50