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	$152.85	4.700%	$160.034	$160.03	$160.05	$160.00
Purchase #2	$157.47	13.130%	$178.1458	$178.15	$178.15	$178.10
Purchase #3	$49.83	11.401%	$55.5111	$55.51	$55.50	$55.50
Purchase #4	$58.44	12.148%	$65.5393	$65.54	$65.55	$65.50
Purchase #5	$227.92	10.511%	$251.8767	$251.88	$251.90	$251.90
Purchase #6	$65.29	5.712%	$69.0194	$69.02	$69.00	$69.00
Purchase #7	$59.63	10.534%	$65.9114	$65.91	$65.90	$65.90
7 purchase totals =	$771.43		$846.0377	$846.04	$846.05	$845.90