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	$67.52	10.349%	$74.5076	$74.51	$74.50	$74.50
Purchase #2	$209.32	11.733%	$233.8795	$233.88	$233.90	$233.90
Purchase #3	$110.64	11.485%	$123.347	$123.35	$123.35	$123.30
Purchase #4	$80.84	10.171%	$89.0622	$89.06	$89.05	$89.10
Purchase #5	$229.38	11.274%	$255.2403	$255.24	$255.25	$255.20
Purchase #6	$232.99	6.172%	$247.3701	$247.37	$247.35	$247.40
Purchase #7	$189.53	7.697%	$204.1181	$204.12	$204.10	$204.10
7 purchase totals =	$1,120.22		$1,227.5248	$1,227.53	$1,227.50	$1,227.50