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	$58.80	5.268%	$61.8976	$61.90	$61.90	$61.90
Purchase #2	$79.95	13.510%	$90.7512	$90.75	$90.75	$90.80
Purchase #3	$5.59	5.738%	$5.9108	$5.91	$5.90	$5.90
Purchase #4	$194.84	4.579%	$203.7617	$203.76	$203.75	$203.80
Purchase #5	$153.48	12.190%	$172.1892	$172.19	$172.20	$172.20
Purchase #6	$92.79	8.583%	$100.7542	$100.75	$100.75	$100.80
Purchase #7	$134.44	4.300%	$140.2209	$140.22	$140.20	$140.20
7 purchase totals =	$719.89		$775.4856	$775.48	$775.45	$775.60