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	$137.29	11.393%	$152.9314	$152.93	$152.95	$152.90
Purchase #2	$79.69	7.353%	$85.5496	$85.55	$85.55	$85.50
Purchase #3	$160.32	11.306%	$178.4458	$178.45	$178.45	$178.40
Purchase #4	$23.94	4.746%	$25.0762	$25.08	$25.10	$25.10
Purchase #5	$192.45	4.322%	$200.7677	$200.77	$200.75	$200.80
Purchase #6	$206.72	7.805%	$222.8545	$222.85	$222.85	$222.90
Purchase #7	$193.26	4.795%	$202.5268	$202.53	$202.55	$202.50
7 purchase totals =	$993.67		$1,068.1520	$1,068.16	$1,068.20	$1,068.10