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	$196.70	11.589%	$219.4956	$219.50	$219.50	$219.50
Purchase #2	$231.66	11.773%	$258.9333	$258.93	$258.95	$258.90
Purchase #3	$75.96	12.550%	$85.493	$85.49	$85.50	$85.50
Purchase #4	$187.52	10.236%	$206.7145	$206.71	$206.70	$206.70
Purchase #5	$234.82	3.590%	$243.25	$243.25	$243.25	$243.30
Purchase #6	$171.81	6.278%	$182.5962	$182.60	$182.60	$182.60
Purchase #7	$209.39	13.136%	$236.8955	$236.90	$236.90	$236.90
7 purchase totals =	$1,307.86		$1,433.3781	$1,433.38	$1,433.40	$1,433.40