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	$164.94	12.192%	$185.0495	$185.05	$185.05	$185.00
Purchase #2	$44.53	12.586%	$50.1345	$50.13	$50.15	$50.10
Purchase #3	$49.27	5.594%	$52.0262	$52.03	$52.05	$52.00
Purchase #4	$233.63	13.611%	$265.4294	$265.43	$265.45	$265.40
Purchase #5	$213.61	4.761%	$223.78	$223.78	$223.80	$223.80
Purchase #6	$83.90	13.253%	$95.0193	$95.02	$95.00	$95.00
Purchase #7	$128.31	6.672%	$136.8708	$136.87	$136.85	$136.90
7 purchase totals =	$918.19		$1,008.3097	$1,008.31	$1,008.35	$1,008.20