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	$207.61	11.312%	$231.0948	$231.09	$231.10	$231.10
Purchase #2	$201.44	10.726%	$223.0465	$223.05	$223.05	$223.00
Purchase #3	$233.88	3.237%	$241.4507	$241.45	$241.45	$241.50
Purchase #4	$62.30	6.864%	$66.5763	$66.58	$66.60	$66.60
Purchase #5	$30.29	7.427%	$32.5396	$32.54	$32.55	$32.50
Purchase #6	$242.60	4.296%	$253.0221	$253.02	$253.00	$253.00
Purchase #7	$134.79	13.608%	$153.1322	$153.13	$153.15	$153.10
7 purchase totals =	$1,112.91		$1,200.8622	$1,200.86	$1,200.90	$1,200.80