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	$248.74	13.725%	$282.8796	$282.88	$282.90	$282.90
Purchase #2	$28.85	3.266%	$29.7922	$29.79	$29.80	$29.80
Purchase #3	$189.65	10.830%	$210.1891	$210.19	$210.20	$210.20
Purchase #4	$190.58	6.715%	$203.3774	$203.38	$203.40	$203.40
Purchase #5	$69.77	5.216%	$73.4092	$73.41	$73.40	$73.40
Purchase #6	$50.96	13.187%	$57.6801	$57.68	$57.70	$57.70
Purchase #7	$152.45	4.594%	$159.4536	$159.45	$159.45	$159.50
7 purchase totals =	$931.00		$1,016.7812	$1,016.78	$1,016.85	$1,016.90