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	$80.32	11.594%	$89.6323	$89.63	$89.65	$89.60
Purchase #2	$191.61	13.638%	$217.7418	$217.74	$217.75	$217.70
Purchase #3	$33.72	5.300%	$35.5072	$35.51	$35.50	$35.50
Purchase #4	$66.47	8.212%	$71.9285	$71.93	$71.95	$71.90
Purchase #5	$58.39	7.367%	$62.6916	$62.69	$62.70	$62.70
Purchase #6	$73.46	5.626%	$77.5929	$77.59	$77.60	$77.60
Purchase #7	$76.59	5.802%	$81.0338	$81.03	$81.05	$81.00
7 purchase totals =	$580.56		$636.1281	$636.12	$636.20	$636.00