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	$169.83	3.387%	$175.5821	$175.58	$175.60	$175.60
Purchase #2	$42.43	7.500%	$45.6123	$45.61	$45.60	$45.60
Purchase #3	$141.81	9.268%	$154.953	$154.95	$154.95	$155.00
Purchase #4	$33.29	13.821%	$37.891	$37.89	$37.90	$37.90
Purchase #5	$117.78	13.203%	$133.3305	$133.33	$133.35	$133.30
Purchase #6	$195.25	9.248%	$213.3067	$213.31	$213.30	$213.30
Purchase #7	$147.28	11.567%	$164.3159	$164.32	$164.30	$164.30
7 purchase totals =	$847.67		$924.9915	$924.99	$925.00	$925.00