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	$54.81	12.182%	$61.487	$61.49	$61.50	$61.50
Purchase #2	$199.99	4.570%	$209.1295	$209.13	$209.15	$209.10
Purchase #3	$225.88	3.496%	$233.7768	$233.78	$233.80	$233.80
Purchase #4	$66.76	9.684%	$73.225	$73.23	$73.25	$73.20
Purchase #5	$154.73	8.781%	$168.3168	$168.32	$168.30	$168.30
Purchase #6	$203.47	11.512%	$226.8935	$226.89	$226.90	$226.90
Purchase #7	$61.34	10.317%	$67.6684	$67.67	$67.65	$67.70
7 purchase totals =	$966.98		$1,040.4970	$1,040.51	$1,040.55	$1,040.50