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	$114.74	11.108%	$127.4853	$127.49	$127.50	$127.50
Purchase #2	$66.34	8.458%	$71.951	$71.95	$71.95	$72.00
Purchase #3	$247.83	4.784%	$259.6862	$259.69	$259.70	$259.70
Purchase #4	$147.57	12.407%	$165.879	$165.88	$165.90	$165.90
Purchase #5	$191.85	5.850%	$203.0732	$203.07	$203.05	$203.10
Purchase #6	$56.54	7.680%	$60.8823	$60.88	$60.90	$60.90
Purchase #7	$171.37	12.826%	$193.3499	$193.35	$193.35	$193.30
7 purchase totals =	$996.24		$1,082.3069	$1,082.31	$1,082.35	$1,082.40