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	$85.27	3.240%	$88.0327	$88.03	$88.05	$88.00
Purchase #2	$103.60	5.175%	$108.9613	$108.96	$108.95	$109.00
Purchase #3	$167.55	5.332%	$176.4838	$176.48	$176.50	$176.50
Purchase #4	$40.60	5.318%	$42.7591	$42.76	$42.75	$42.80
Purchase #5	$69.82	12.435%	$78.5021	$78.50	$78.50	$78.50
Purchase #6	$45.41	13.390%	$51.4904	$51.49	$51.50	$51.50
Purchase #7	$26.61	13.286%	$30.1454	$30.15	$30.15	$30.10
7 purchase totals =	$538.86		$576.3748	$576.37	$576.40	$576.40