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	$91.87	8.167%	$99.373	$99.37	$99.35	$99.40
Purchase #2	$191.94	3.797%	$199.228	$199.23	$199.25	$199.20
Purchase #3	$214.48	4.628%	$224.4061	$224.41	$224.40	$224.40
Purchase #4	$128.85	8.213%	$139.4325	$139.43	$139.45	$139.40
Purchase #5	$85.98	6.408%	$91.4896	$91.49	$91.50	$91.50
Purchase #6	$42.40	6.243%	$45.047	$45.05	$45.05	$45.00
Purchase #7	$212.90	3.814%	$221.02	$221.02	$221.00	$221.00
7 purchase totals =	$968.42		$1,019.9962	$1,020.00	$1,020.00	$1,019.90