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	$79.42	7.441%	$85.3296	$85.33	$85.35	$85.30
Purchase #2	$203.59	13.542%	$231.1602	$231.16	$231.15	$231.20
Purchase #3	$219.30	10.565%	$242.469	$242.47	$242.45	$242.50
Purchase #4	$90.77	11.765%	$101.4491	$101.45	$101.45	$101.40
Purchase #5	$10.65	13.184%	$12.0541	$12.05	$12.05	$12.10
Purchase #6	$141.50	13.346%	$160.3846	$160.38	$160.40	$160.40
Purchase #7	$165.45	3.277%	$170.8718	$170.87	$170.85	$170.90
7 purchase totals =	$910.68		$1,003.7184	$1,003.71	$1,003.70	$1,003.80