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	$133.34	13.168%	$150.8982	$150.90	$150.90	$150.90
Purchase #2	$193.74	11.712%	$216.4308	$216.43	$216.45	$216.40
Purchase #3	$54.47	4.740%	$57.0519	$57.05	$57.05	$57.10
Purchase #4	$90.86	11.148%	$100.9891	$100.99	$101.00	$101.00
Purchase #5	$11.87	4.647%	$12.4216	$12.42	$12.40	$12.40
Purchase #6	$209.52	10.428%	$231.3687	$231.37	$231.35	$231.40
Purchase #7	$36.58	10.138%	$40.2885	$40.29	$40.30	$40.30
7 purchase totals =	$730.38		$809.4488	$809.45	$809.45	$809.50