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	$152.62	6.712%	$162.8639	$162.86	$162.85	$162.90
Purchase #2	$124.43	8.419%	$134.9058	$134.91	$134.90	$134.90
Purchase #3	$57.87	6.540%	$61.6547	$61.65	$61.65	$61.70
Purchase #4	$132.67	11.342%	$147.7174	$147.72	$147.70	$147.70
Purchase #5	$67.88	7.744%	$73.1366	$73.14	$73.15	$73.10
Purchase #6	$118.89	6.237%	$126.3052	$126.31	$126.30	$126.30
Purchase #7	$64.52	11.538%	$71.9643	$71.96	$71.95	$72.00
7 purchase totals =	$718.88		$778.5479	$778.55	$778.50	$778.60