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	$44.75	4.706%	$46.8559	$46.86	$46.85	$46.90
Purchase #2	$225.95	13.443%	$256.3245	$256.32	$256.30	$256.30
Purchase #3	$144.31	6.653%	$153.9109	$153.91	$153.90	$153.90
Purchase #4	$8.81	8.460%	$9.5553	$9.56	$9.55	$9.60
Purchase #5	$59.27	9.454%	$64.8734	$64.87	$64.85	$64.90
Purchase #6	$140.87	7.300%	$151.1535	$151.15	$151.15	$151.20
Purchase #7	$185.86	5.693%	$196.441	$196.44	$196.45	$196.40
7 purchase totals =	$809.82		$879.1145	$879.11	$879.05	$879.20