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	$167.26	10.579%	$184.9544	$184.95	$184.95	$185.00
Purchase #2	$212.34	4.656%	$222.2266	$222.23	$222.25	$222.20
Purchase #3	$173.47	11.179%	$192.8622	$192.86	$192.85	$192.90
Purchase #4	$246.84	10.733%	$273.3333	$273.33	$273.35	$273.30
Purchase #5	$78.39	13.597%	$89.0487	$89.05	$89.05	$89.00
Purchase #6	$106.91	11.765%	$119.488	$119.49	$119.50	$119.50
Purchase #7	$246.94	3.469%	$255.5063	$255.51	$255.50	$255.50
7 purchase totals =	$1,232.15		$1,337.4195	$1,337.42	$1,337.45	$1,337.40