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	$197.89	3.552%	$204.9191	$204.92	$204.90	$204.90
Purchase #2	$91.69	5.241%	$96.4955	$96.50	$96.50	$96.50
Purchase #3	$36.95	8.664%	$40.1513	$40.15	$40.15	$40.20
Purchase #4	$228.66	11.159%	$254.1762	$254.18	$254.20	$254.20
Purchase #5	$66.39	5.668%	$70.153	$70.15	$70.15	$70.20
Purchase #6	$177.72	10.333%	$196.0838	$196.08	$196.10	$196.10
Purchase #7	$74.47	11.148%	$82.7719	$82.77	$82.75	$82.80
7 purchase totals =	$873.77		$944.7508	$944.75	$944.75	$944.90