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	$71.55	5.344%	$75.3736	$75.37	$75.35	$75.40
Purchase #2	$82.90	4.827%	$86.9016	$86.90	$86.90	$86.90
Purchase #3	$59.80	4.866%	$62.7099	$62.71	$62.70	$62.70
Purchase #4	$178.48	3.555%	$184.825	$184.83	$184.85	$184.80
Purchase #5	$73.81	11.594%	$82.3675	$82.37	$82.35	$82.40
Purchase #6	$73.55	13.395%	$83.402	$83.40	$83.40	$83.40
Purchase #7	$59.70	7.255%	$64.0312	$64.03	$64.05	$64.00
7 purchase totals =	$599.79		$639.6108	$639.61	$639.60	$639.60