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	$14.34	7.826%	$15.4622	$15.46	$15.45	$15.50
Purchase #2	$37.61	5.188%	$39.5612	$39.56	$39.55	$39.60
Purchase #3	$98.88	12.639%	$111.3774	$111.38	$111.40	$111.40
Purchase #4	$65.31	9.220%	$71.3316	$71.33	$71.35	$71.30
Purchase #5	$174.45	9.409%	$190.864	$190.86	$190.85	$190.90
Purchase #6	$245.68	3.353%	$253.9177	$253.92	$253.90	$253.90
Purchase #7	$48.70	3.213%	$50.2647	$50.26	$50.25	$50.30
7 purchase totals =	$684.97		$732.7788	$732.77	$732.75	$732.90