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	$114.45	13.773%	$130.2132	$130.21	$130.20	$130.20
Purchase #2	$131.32	13.349%	$148.8499	$148.85	$148.85	$148.80
Purchase #3	$62.31	5.294%	$65.6087	$65.61	$65.60	$65.60
Purchase #4	$37.80	4.383%	$39.4568	$39.46	$39.45	$39.50
Purchase #5	$82.67	9.758%	$90.7369	$90.74	$90.75	$90.70
Purchase #6	$116.76	6.589%	$124.4533	$124.45	$124.45	$124.50
Purchase #7	$185.71	5.262%	$195.4821	$195.48	$195.50	$195.50
7 purchase totals =	$731.02		$794.8009	$794.80	$794.80	$794.80