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	$222.91	9.705%	$244.5434	$244.54	$244.55	$244.50
Purchase #2	$7.67	7.540%	$8.2483	$8.25	$8.25	$8.20
Purchase #3	$106.41	6.648%	$113.4841	$113.48	$113.50	$113.50
Purchase #4	$21.93	9.517%	$24.0171	$24.02	$24.00	$24.00
Purchase #5	$112.85	10.152%	$124.3065	$124.31	$124.30	$124.30
Purchase #6	$90.53	10.800%	$100.3072	$100.31	$100.30	$100.30
Purchase #7	$133.54	13.263%	$151.2514	$151.25	$151.25	$151.30
7 purchase totals =	$695.84		$766.1580	$766.16	$766.15	$766.10