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	$90.76	4.501%	$94.8451	$94.85	$94.85	$94.80
Purchase #2	$156.41	7.744%	$168.5224	$168.52	$168.50	$168.50
Purchase #3	$70.63	3.843%	$73.3443	$73.34	$73.35	$73.30
Purchase #4	$76.41	6.740%	$81.56	$81.56	$81.55	$81.60
Purchase #5	$99.51	11.655%	$111.1079	$111.11	$111.10	$111.10
Purchase #6	$65.54	13.621%	$74.4672	$74.47	$74.45	$74.50
Purchase #7	$143.65	7.589%	$154.5516	$154.55	$154.55	$154.60
7 purchase totals =	$702.91		$758.3985	$758.40	$758.35	$758.40