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	$174.79	12.421%	$196.5007	$196.50	$196.50	$196.50
Purchase #2	$43.35	9.778%	$47.5888	$47.59	$47.60	$47.60
Purchase #3	$249.64	4.868%	$261.7925	$261.79	$261.80	$261.80
Purchase #4	$60.68	10.108%	$66.8135	$66.81	$66.80	$66.80
Purchase #5	$9.32	11.830%	$10.4226	$10.42	$10.40	$10.40
Purchase #6	$78.94	6.138%	$83.7853	$83.79	$83.80	$83.80
Purchase #7	$247.40	11.339%	$275.4527	$275.45	$275.45	$275.50
7 purchase totals =	$864.12		$942.3561	$942.35	$942.35	$942.40