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	$105.29	6.622%	$112.2623	$112.26	$112.25	$112.30
Purchase #2	$229.38	9.355%	$250.8385	$250.84	$250.85	$250.80
Purchase #3	$116.82	6.743%	$124.6972	$124.70	$124.70	$124.70
Purchase #4	$170.82	6.348%	$181.6637	$181.66	$181.65	$181.70
Purchase #5	$54.69	9.385%	$59.8227	$59.82	$59.80	$59.80
Purchase #6	$211.85	9.505%	$231.9863	$231.99	$232.00	$232.00
Purchase #7	$48.72	11.421%	$54.2843	$54.28	$54.30	$54.30
7 purchase totals =	$937.57		$1,015.5550	$1,015.55	$1,015.55	$1,015.60