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	$178.88	9.467%	$195.8146	$195.81	$195.80	$195.80
Purchase #2	$90.57	5.732%	$95.7615	$95.76	$95.75	$95.80
Purchase #3	$15.38	12.517%	$17.3051	$17.31	$17.30	$17.30
Purchase #4	$71.54	7.446%	$76.8669	$76.87	$76.85	$76.90
Purchase #5	$107.77	3.179%	$111.196	$111.20	$111.20	$111.20
Purchase #6	$40.67	12.235%	$45.646	$45.65	$45.65	$45.60
Purchase #7	$188.59	4.218%	$196.5447	$196.54	$196.55	$196.50
7 purchase totals =	$693.40		$739.1348	$739.14	$739.10	$739.10