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	$106.61	4.645%	$111.562	$111.56	$111.55	$111.60
Purchase #2	$91.54	3.846%	$95.0606	$95.06	$95.05	$95.10
Purchase #3	$10.27	7.462%	$11.0363	$11.04	$11.05	$11.00
Purchase #4	$229.69	5.427%	$242.1553	$242.16	$242.15	$242.20
Purchase #5	$129.55	13.694%	$147.2906	$147.29	$147.30	$147.30
Purchase #6	$139.80	9.490%	$153.067	$153.07	$153.05	$153.10
Purchase #7	$181.80	4.782%	$190.4937	$190.49	$190.50	$190.50
7 purchase totals =	$889.26		$950.6655	$950.67	$950.65	$950.80