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	$14.41	4.657%	$15.0811	$15.08	$15.10	$15.10
Purchase #2	$221.52	4.317%	$231.083	$231.08	$231.10	$231.10
Purchase #3	$179.58	5.344%	$189.1768	$189.18	$189.20	$189.20
Purchase #4	$242.50	13.140%	$274.3645	$274.36	$274.35	$274.40
Purchase #5	$185.52	8.196%	$200.7252	$200.73	$200.75	$200.70
Purchase #6	$71.34	4.434%	$74.5032	$74.50	$74.50	$74.50
Purchase #7	$78.48	13.484%	$89.0622	$89.06	$89.05	$89.10
7 purchase totals =	$993.35		$1,073.9960	$1,073.99	$1,074.05	$1,074.10