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	$191.32	7.801%	$206.2449	$206.24	$206.25	$206.20
Purchase #2	$134.34	8.516%	$145.7804	$145.78	$145.80	$145.80
Purchase #3	$50.43	5.300%	$53.1028	$53.10	$53.10	$53.10
Purchase #4	$210.33	13.417%	$238.55	$238.55	$238.55	$238.60
Purchase #5	$228.36	11.308%	$254.1829	$254.18	$254.20	$254.20
Purchase #6	$235.80	6.850%	$251.9523	$251.95	$251.95	$252.00
Purchase #7	$94.43	11.613%	$105.3962	$105.40	$105.40	$105.40
7 purchase totals =	$1,145.01		$1,255.2095	$1,255.20	$1,255.25	$1,255.30