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	$147.44	3.700%	$152.8953	$152.90	$152.90	$152.90
Purchase #2	$92.99	6.694%	$99.2148	$99.21	$99.20	$99.20
Purchase #3	$63.85	3.419%	$66.033	$66.03	$66.05	$66.00
Purchase #4	$152.35	8.472%	$165.2571	$165.26	$165.25	$165.30
Purchase #5	$76.61	12.460%	$86.1556	$86.16	$86.15	$86.20
Purchase #6	$217.58	7.367%	$233.6091	$233.61	$233.60	$233.60
Purchase #7	$182.84	9.513%	$200.2336	$200.23	$200.25	$200.20
7 purchase totals =	$933.66		$1,003.3985	$1,003.40	$1,003.40	$1,003.40