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	$55.79	4.578%	$58.3441	$58.34	$58.35	$58.30
Purchase #2	$64.45	13.122%	$72.9071	$72.91	$72.90	$72.90
Purchase #3	$68.86	5.556%	$72.6859	$72.69	$72.70	$72.70
Purchase #4	$66.40	10.587%	$73.4298	$73.43	$73.45	$73.40
Purchase #5	$84.29	10.619%	$93.2408	$93.24	$93.25	$93.20
Purchase #6	$108.52	3.785%	$112.6275	$112.63	$112.65	$112.60
Purchase #7	$201.55	10.222%	$222.1524	$222.15	$222.15	$222.20
7 purchase totals =	$649.86		$705.3876	$705.39	$705.45	$705.30