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	$246.79	6.344%	$262.4464	$262.45	$262.45	$262.40
Purchase #2	$30.78	10.137%	$33.9002	$33.90	$33.90	$33.90
Purchase #3	$174.46	9.439%	$190.9273	$190.93	$190.95	$190.90
Purchase #4	$30.93	8.593%	$33.5878	$33.59	$33.60	$33.60
Purchase #5	$98.28	11.506%	$109.5881	$109.59	$109.60	$109.60
Purchase #6	$93.64	4.478%	$97.8332	$97.83	$97.85	$97.80
Purchase #7	$201.78	10.129%	$222.2183	$222.22	$222.20	$222.20
7 purchase totals =	$876.66		$950.5013	$950.51	$950.55	$950.40