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	$237.52	6.762%	$253.5811	$253.58	$253.60	$253.60
Purchase #2	$89.97	11.243%	$100.0853	$100.09	$100.10	$100.10
Purchase #3	$64.71	3.571%	$67.0208	$67.02	$67.00	$67.00
Purchase #4	$230.33	11.637%	$257.1335	$257.13	$257.15	$257.10
Purchase #5	$113.73	3.262%	$117.4399	$117.44	$117.45	$117.40
Purchase #6	$120.63	6.548%	$128.5289	$128.53	$128.55	$128.50
Purchase #7	$213.89	9.151%	$233.4631	$233.46	$233.45	$233.50
7 purchase totals =	$1,070.78		$1,157.2526	$1,157.25	$1,157.30	$1,157.20