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	$91.72	5.679%	$96.9288	$96.93	$96.95	$96.90
Purchase #2	$130.79	11.841%	$146.2768	$146.28	$146.30	$146.30
Purchase #3	$130.63	8.804%	$142.1307	$142.13	$142.15	$142.10
Purchase #4	$212.28	12.548%	$238.9169	$238.92	$238.90	$238.90
Purchase #5	$168.38	6.797%	$179.8248	$179.82	$179.80	$179.80
Purchase #6	$11.43	6.248%	$12.1441	$12.14	$12.15	$12.10
Purchase #7	$63.37	4.370%	$66.1393	$66.14	$66.15	$66.10
7 purchase totals =	$808.60		$882.3614	$882.36	$882.40	$882.20