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	$98.58	12.739%	$111.1381	$111.14	$111.15	$111.10
Purchase #2	$34.84	7.225%	$37.3572	$37.36	$37.35	$37.40
Purchase #3	$243.81	10.436%	$269.254	$269.25	$269.25	$269.30
Purchase #4	$130.95	4.763%	$137.1871	$137.19	$137.20	$137.20
Purchase #5	$43.35	4.211%	$45.1755	$45.18	$45.20	$45.20
Purchase #6	$238.46	6.375%	$253.6618	$253.66	$253.65	$253.70
Purchase #7	$39.56	10.145%	$43.5734	$43.57	$43.55	$43.60
7 purchase totals =	$829.55		$897.3471	$897.35	$897.35	$897.50