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	$141.40	10.373%	$156.0674	$156.07	$156.05	$156.10
Purchase #2	$201.68	13.612%	$229.1327	$229.13	$229.15	$229.10
Purchase #3	$40.57	3.607%	$42.0334	$42.03	$42.05	$42.00
Purchase #4	$85.63	11.499%	$95.4766	$95.48	$95.50	$95.50
Purchase #5	$68.45	13.634%	$77.7825	$77.78	$77.80	$77.80
Purchase #6	$180.82	13.569%	$205.3555	$205.36	$205.35	$205.40
Purchase #7	$72.26	8.200%	$78.1853	$78.19	$78.20	$78.20
7 purchase totals =	$790.81		$884.0334	$884.04	$884.10	$884.10