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	$185.55	3.169%	$191.4301	$191.43	$191.45	$191.40
Purchase #2	$181.57	5.651%	$191.8305	$191.83	$191.85	$191.80
Purchase #3	$101.82	9.473%	$111.4654	$111.47	$111.45	$111.50
Purchase #4	$173.54	9.234%	$189.5647	$189.56	$189.55	$189.60
Purchase #5	$14.80	12.370%	$16.6308	$16.63	$16.65	$16.60
Purchase #6	$228.29	5.528%	$240.9099	$240.91	$240.90	$240.90
Purchase #7	$37.96	10.363%	$41.8938	$41.89	$41.90	$41.90
7 purchase totals =	$923.53		$983.7252	$983.72	$983.75	$983.70