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	$133.33	12.754%	$150.3349	$150.33	$150.35	$150.30
Purchase #2	$130.78	13.560%	$148.5138	$148.51	$148.50	$148.50
Purchase #3	$32.69	9.470%	$35.7857	$35.79	$35.80	$35.80
Purchase #4	$206.94	7.788%	$223.0565	$223.06	$223.05	$223.10
Purchase #5	$143.79	8.104%	$155.4427	$155.44	$155.45	$155.40
Purchase #6	$67.33	13.688%	$76.5461	$76.55	$76.55	$76.50
Purchase #7	$225.53	12.357%	$253.3987	$253.40	$253.40	$253.40
7 purchase totals =	$940.39		$1,043.0784	$1,043.08	$1,043.10	$1,043.00