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	$89.74	4.222%	$93.5288	$93.53	$93.55	$93.50
Purchase #2	$220.73	5.778%	$233.4838	$233.48	$233.50	$233.50
Purchase #3	$226.40	12.670%	$255.0849	$255.08	$255.10	$255.10
Purchase #4	$219.73	12.395%	$246.9655	$246.97	$246.95	$247.00
Purchase #5	$73.36	12.688%	$82.6679	$82.67	$82.65	$82.70
Purchase #6	$140.33	8.406%	$152.1261	$152.13	$152.15	$152.10
Purchase #7	$110.98	4.850%	$116.3625	$116.36	$116.35	$116.40
7 purchase totals =	$1,081.27		$1,180.2195	$1,180.22	$1,180.25	$1,180.30