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	$232.84	3.773%	$241.6251	$241.63	$241.65	$241.60
Purchase #2	$42.80	12.534%	$48.1646	$48.16	$48.15	$48.20
Purchase #3	$73.70	9.673%	$80.829	$80.83	$80.85	$80.80
Purchase #4	$34.41	7.339%	$36.9353	$36.94	$36.95	$36.90
Purchase #5	$34.31	8.563%	$37.248	$37.25	$37.25	$37.20
Purchase #6	$131.26	11.124%	$145.8614	$145.86	$145.85	$145.90
Purchase #7	$80.79	6.325%	$85.9	$85.90	$85.90	$85.90
7 purchase totals =	$630.11		$676.5634	$676.57	$676.60	$676.50