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	$86.69	11.825%	$96.9411	$96.94	$96.95	$96.90
Purchase #2	$36.25	5.175%	$38.1259	$38.13	$38.15	$38.10
Purchase #3	$56.67	4.560%	$59.2542	$59.25	$59.25	$59.30
Purchase #4	$54.49	13.310%	$61.7426	$61.74	$61.75	$61.70
Purchase #5	$66.98	11.507%	$74.6874	$74.69	$74.70	$74.70
Purchase #6	$135.27	3.152%	$139.5337	$139.53	$139.55	$139.50
Purchase #7	$30.98	10.451%	$34.2177	$34.22	$34.20	$34.20
7 purchase totals =	$467.33		$504.5026	$504.50	$504.55	$504.40