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	$86.54	5.671%	$91.4477	$91.45	$91.45	$91.40
Purchase #2	$67.79	5.648%	$71.6188	$71.62	$71.60	$71.60
Purchase #3	$45.81	7.247%	$49.1299	$49.13	$49.15	$49.10
Purchase #4	$225.89	9.562%	$247.4896	$247.49	$247.50	$247.50
Purchase #5	$168.74	11.404%	$187.9831	$187.98	$188.00	$188.00
Purchase #6	$100.67	3.419%	$104.1119	$104.11	$104.10	$104.10
Purchase #7	$122.51	4.113%	$127.5488	$127.55	$127.55	$127.50
7 purchase totals =	$817.95		$879.3298	$879.33	$879.35	$879.20