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	$29.51	13.595%	$33.5219	$33.52	$33.50	$33.50
Purchase #2	$90.74	6.677%	$96.7987	$96.80	$96.80	$96.80
Purchase #3	$78.84	6.634%	$84.0702	$84.07	$84.05	$84.10
Purchase #4	$232.73	6.320%	$247.4385	$247.44	$247.45	$247.40
Purchase #5	$39.82	13.413%	$45.1611	$45.16	$45.15	$45.20
Purchase #6	$109.39	12.629%	$123.2049	$123.20	$123.20	$123.20
Purchase #7	$185.64	5.813%	$196.4313	$196.43	$196.45	$196.40
7 purchase totals =	$766.67		$826.6266	$826.62	$826.60	$826.60