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	$223.43	4.363%	$233.1783	$233.18	$233.20	$233.20
Purchase #2	$20.33	11.482%	$22.6643	$22.66	$22.65	$22.70
Purchase #3	$156.86	11.653%	$175.1389	$175.14	$175.15	$175.10
Purchase #4	$54.89	13.552%	$62.3287	$62.33	$62.35	$62.30
Purchase #5	$137.77	10.546%	$152.2992	$152.30	$152.30	$152.30
Purchase #6	$163.62	4.580%	$171.1138	$171.11	$171.10	$171.10
Purchase #7	$59.30	11.825%	$66.3122	$66.31	$66.30	$66.30
7 purchase totals =	$816.20		$883.0354	$883.03	$883.05	$883.00