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	$42.59	6.118%	$45.1957	$45.20	$45.20	$45.20
Purchase #2	$85.85	4.715%	$89.8978	$89.90	$89.90	$89.90
Purchase #3	$166.60	9.734%	$182.8168	$182.82	$182.80	$182.80
Purchase #4	$88.51	7.343%	$95.0093	$95.01	$95.00	$95.00
Purchase #5	$222.97	9.525%	$244.2079	$244.21	$244.20	$244.20
Purchase #6	$112.27	7.653%	$120.862	$120.86	$120.85	$120.90
Purchase #7	$112.52	4.174%	$117.2166	$117.22	$117.20	$117.20
7 purchase totals =	$831.31		$895.2061	$895.22	$895.15	$895.20