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	$69.37	6.577%	$73.9325	$73.93	$73.95	$73.90
Purchase #2	$73.39	12.204%	$82.3465	$82.35	$82.35	$82.30
Purchase #3	$168.61	9.746%	$185.0427	$185.04	$185.05	$185.00
Purchase #4	$204.57	8.675%	$222.3164	$222.32	$222.30	$222.30
Purchase #5	$145.90	7.324%	$156.5857	$156.59	$156.60	$156.60
Purchase #6	$144.70	8.536%	$157.0516	$157.05	$157.05	$157.10
Purchase #7	$238.27	3.667%	$247.0074	$247.01	$247.00	$247.00
7 purchase totals =	$1,044.81		$1,124.2828	$1,124.29	$1,124.30	$1,124.20