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	$193.89	8.160%	$209.7114	$209.71	$209.70	$209.70
Purchase #2	$99.48	12.385%	$111.8006	$111.80	$111.80	$111.80
Purchase #3	$57.65	8.156%	$62.3519	$62.35	$62.35	$62.40
Purchase #4	$228.43	13.315%	$258.8455	$258.85	$258.85	$258.80
Purchase #5	$120.59	8.787%	$131.1862	$131.19	$131.20	$131.20
Purchase #6	$202.89	11.211%	$225.636	$225.64	$225.65	$225.60
Purchase #7	$26.45	13.155%	$29.9295	$29.93	$29.95	$29.90
7 purchase totals =	$929.38		$1,029.4611	$1,029.47	$1,029.50	$1,029.40