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	$141.34	6.306%	$150.2529	$150.25	$150.25	$150.30
Purchase #2	$170.60	8.463%	$185.0379	$185.04	$185.05	$185.00
Purchase #3	$189.82	11.517%	$211.6816	$211.68	$211.70	$211.70
Purchase #4	$55.68	6.563%	$59.3343	$59.33	$59.35	$59.30
Purchase #5	$14.87	13.316%	$16.8501	$16.85	$16.85	$16.90
Purchase #6	$60.38	9.397%	$66.0539	$66.05	$66.05	$66.10
Purchase #7	$106.44	5.781%	$112.5933	$112.59	$112.60	$112.60
7 purchase totals =	$739.13		$801.8040	$801.79	$801.85	$801.90