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	$137.78	7.674%	$148.3532	$148.35	$148.35	$148.40
Purchase #2	$110.84	4.758%	$116.1138	$116.11	$116.10	$116.10
Purchase #3	$125.31	13.528%	$142.2619	$142.26	$142.25	$142.30
Purchase #4	$178.80	6.523%	$190.4631	$190.46	$190.45	$190.50
Purchase #5	$176.80	4.614%	$184.9576	$184.96	$184.95	$185.00
Purchase #6	$123.25	13.710%	$140.1476	$140.15	$140.15	$140.10
Purchase #7	$223.27	3.869%	$231.9083	$231.91	$231.90	$231.90
7 purchase totals =	$1,076.05		$1,154.2055	$1,154.20	$1,154.15	$1,154.30