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	$178.38	5.827%	$188.7742	$188.77	$188.75	$188.80
Purchase #2	$155.65	10.729%	$172.3497	$172.35	$172.35	$172.30
Purchase #3	$212.48	5.481%	$224.126	$224.13	$224.15	$224.10
Purchase #4	$10.51	13.249%	$11.9025	$11.90	$11.90	$11.90
Purchase #5	$217.57	10.318%	$240.0189	$240.02	$240.00	$240.00
Purchase #6	$79.59	6.828%	$85.0244	$85.02	$85.00	$85.00
Purchase #7	$137.83	13.564%	$156.5253	$156.53	$156.55	$156.50
7 purchase totals =	$992.01		$1,078.7210	$1,078.72	$1,078.70	$1,078.60