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	$206.25	8.354%	$223.4801	$223.48	$223.50	$223.50
Purchase #2	$142.27	5.243%	$149.7292	$149.73	$149.75	$149.70
Purchase #3	$201.77	9.327%	$220.5891	$220.59	$220.60	$220.60
Purchase #4	$200.55	6.620%	$213.8264	$213.83	$213.85	$213.80
Purchase #5	$28.53	12.255%	$32.0264	$32.03	$32.05	$32.00
Purchase #6	$241.29	6.323%	$256.5468	$256.55	$256.55	$256.50
Purchase #7	$144.76	9.569%	$158.6121	$158.61	$158.60	$158.60
7 purchase totals =	$1,165.42		$1,254.8101	$1,254.82	$1,254.90	$1,254.70