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	$144.90	6.318%	$154.0548	$154.05	$154.05	$154.10
Purchase #2	$29.44	11.574%	$32.8474	$32.85	$32.85	$32.80
Purchase #3	$185.35	3.672%	$192.1561	$192.16	$192.15	$192.20
Purchase #4	$150.69	12.184%	$169.0501	$169.05	$169.05	$169.10
Purchase #5	$100.99	10.801%	$111.8979	$111.90	$111.90	$111.90
Purchase #6	$12.97	3.239%	$13.3901	$13.39	$13.40	$13.40
Purchase #7	$203.96	3.394%	$210.8824	$210.88	$210.90	$210.90
7 purchase totals =	$828.30		$884.2788	$884.28	$884.30	$884.40