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	$40.86	13.766%	$46.4848	$46.48	$46.50	$46.50
Purchase #2	$119.45	7.371%	$128.2547	$128.25	$128.25	$128.30
Purchase #3	$94.53	3.718%	$98.0446	$98.04	$98.05	$98.00
Purchase #4	$248.31	10.863%	$275.2839	$275.28	$275.30	$275.30
Purchase #5	$166.46	10.704%	$184.2779	$184.28	$184.30	$184.30
Purchase #6	$140.25	11.389%	$156.2231	$156.22	$156.20	$156.20
Purchase #7	$154.63	9.135%	$168.7555	$168.76	$168.75	$168.80
7 purchase totals =	$964.49		$1,057.3245	$1,057.31	$1,057.35	$1,057.40