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	$230.51	8.691%	$250.5436	$250.54	$250.55	$250.50
Purchase #2	$247.56	9.673%	$271.5065	$271.51	$271.50	$271.50
Purchase #3	$85.40	8.148%	$92.3584	$92.36	$92.35	$92.40
Purchase #4	$50.79	11.688%	$56.7263	$56.73	$56.75	$56.70
Purchase #5	$95.81	9.729%	$105.1314	$105.13	$105.15	$105.10
Purchase #6	$240.31	13.560%	$272.896	$272.90	$272.90	$272.90
Purchase #7	$22.77	11.243%	$25.33	$25.33	$25.35	$25.30
7 purchase totals =	$973.15		$1,074.4922	$1,074.50	$1,074.55	$1,074.40