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	$160.67	11.505%	$179.1551	$179.16	$179.15	$179.20
Purchase #2	$115.73	11.753%	$129.3317	$129.33	$129.35	$129.30
Purchase #3	$78.87	6.653%	$84.1172	$84.12	$84.10	$84.10
Purchase #4	$250.87	5.245%	$264.0281	$264.03	$264.05	$264.00
Purchase #5	$116.55	8.872%	$126.8903	$126.89	$126.90	$126.90
Purchase #6	$79.74	13.219%	$90.2808	$90.28	$90.30	$90.30
Purchase #7	$141.88	6.731%	$151.4299	$151.43	$151.45	$151.40
7 purchase totals =	$944.31		$1,025.2331	$1,025.24	$1,025.30	$1,025.20