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	$40.61	6.500%	$43.2497	$43.25	$43.25	$43.20
Purchase #2	$8.97	12.562%	$10.0968	$10.10	$10.10	$10.10
Purchase #3	$166.76	8.776%	$181.3949	$181.39	$181.40	$181.40
Purchase #4	$33.77	11.140%	$37.532	$37.53	$37.55	$37.50
Purchase #5	$156.41	11.394%	$174.2314	$174.23	$174.25	$174.20
Purchase #6	$229.36	13.390%	$260.0713	$260.07	$260.05	$260.10
Purchase #7	$117.88	12.425%	$132.5266	$132.53	$132.55	$132.50
7 purchase totals =	$753.76		$839.1027	$839.10	$839.15	$839.00