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	$211.93	3.651%	$219.6676	$219.67	$219.65	$219.70
Purchase #2	$140.83	8.248%	$152.4457	$152.45	$152.45	$152.40
Purchase #3	$229.25	8.261%	$248.1883	$248.19	$248.20	$248.20
Purchase #4	$14.81	10.170%	$16.3162	$16.32	$16.30	$16.30
Purchase #5	$234.57	3.218%	$242.1185	$242.12	$242.10	$242.10
Purchase #6	$62.43	5.547%	$65.893	$65.89	$65.90	$65.90
Purchase #7	$98.88	12.718%	$111.4556	$111.46	$111.45	$111.50
7 purchase totals =	$992.70		$1,056.0849	$1,056.10	$1,056.05	$1,056.10