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	$193.62	12.196%	$217.2339	$217.23	$217.25	$217.20
Purchase #2	$34.64	8.435%	$37.5619	$37.56	$37.55	$37.60
Purchase #3	$53.61	4.391%	$55.964	$55.96	$55.95	$56.00
Purchase #4	$61.39	5.328%	$64.6609	$64.66	$64.65	$64.70
Purchase #5	$247.46	13.411%	$280.6469	$280.65	$280.65	$280.60
Purchase #6	$180.53	6.137%	$191.6091	$191.61	$191.60	$191.60
Purchase #7	$30.49	9.314%	$33.3298	$33.33	$33.35	$33.30
7 purchase totals =	$801.74		$881.0065	$881.00	$881.00	$881.00