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	$146.92	3.475%	$152.0255	$152.03	$152.05	$152.00
Purchase #2	$59.39	4.113%	$61.8327	$61.83	$61.85	$61.80
Purchase #3	$138.95	9.709%	$152.4407	$152.44	$152.45	$152.40
Purchase #4	$124.51	9.426%	$136.2463	$136.25	$136.25	$136.20
Purchase #5	$175.47	5.144%	$184.4962	$184.50	$184.50	$184.50
Purchase #6	$69.64	3.703%	$72.2188	$72.22	$72.20	$72.20
Purchase #7	$235.69	7.825%	$254.1327	$254.13	$254.15	$254.10
7 purchase totals =	$950.57		$1,013.3929	$1,013.40	$1,013.45	$1,013.20