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	$39.94	3.412%	$41.3028	$41.30	$41.30	$41.30
Purchase #2	$177.38	4.817%	$185.9244	$185.92	$185.90	$185.90
Purchase #3	$86.40	13.791%	$98.3154	$98.32	$98.30	$98.30
Purchase #4	$123.95	7.124%	$132.7802	$132.78	$132.80	$132.80
Purchase #5	$177.69	3.756%	$184.364	$184.36	$184.35	$184.40
Purchase #6	$40.35	4.808%	$42.29	$42.29	$42.30	$42.30
Purchase #7	$246.75	6.442%	$262.6456	$262.65	$262.65	$262.60
7 purchase totals =	$892.46		$947.6224	$947.62	$947.60	$947.60