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	$125.86	3.434%	$130.182	$130.18	$130.20	$130.20
Purchase #2	$128.29	11.224%	$142.6893	$142.69	$142.70	$142.70
Purchase #3	$200.56	4.531%	$209.6474	$209.65	$209.65	$209.60
Purchase #4	$36.47	3.851%	$37.8745	$37.87	$37.85	$37.90
Purchase #5	$75.96	10.377%	$83.8424	$83.84	$83.85	$83.80
Purchase #6	$98.97	10.256%	$109.1204	$109.12	$109.10	$109.10
Purchase #7	$229.53	6.413%	$244.2498	$244.25	$244.25	$244.20
7 purchase totals =	$895.64		$957.6058	$957.60	$957.60	$957.50