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	$61.33	6.196%	$65.13	$65.13	$65.15	$65.10
Purchase #2	$214.89	4.855%	$225.3229	$225.32	$225.30	$225.30
Purchase #3	$107.37	8.250%	$116.228	$116.23	$116.25	$116.20
Purchase #4	$196.66	9.333%	$215.0143	$215.01	$215.00	$215.00
Purchase #5	$114.56	13.648%	$130.1951	$130.20	$130.20	$130.20
Purchase #6	$36.77	8.173%	$39.7752	$39.78	$39.80	$39.80
Purchase #7	$100.33	3.758%	$104.1004	$104.10	$104.10	$104.10
7 purchase totals =	$831.91		$895.7659	$895.77	$895.80	$895.70