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	$217.41	6.339%	$231.1916	$231.19	$231.20	$231.20
Purchase #2	$147.88	7.183%	$158.5022	$158.50	$158.50	$158.50
Purchase #3	$55.67	3.832%	$57.8033	$57.80	$57.80	$57.80
Purchase #4	$152.72	9.736%	$167.5888	$167.59	$167.60	$167.60
Purchase #5	$151.47	11.744%	$169.2586	$169.26	$169.25	$169.30
Purchase #6	$144.53	7.874%	$155.9103	$155.91	$155.90	$155.90
Purchase #7	$84.86	10.342%	$93.6362	$93.64	$93.65	$93.60
7 purchase totals =	$954.54		$1,033.8910	$1,033.89	$1,033.90	$1,033.90