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	$227.37	8.475%	$246.6396	$246.64	$246.65	$246.60
Purchase #2	$197.77	7.497%	$212.5968	$212.60	$212.60	$212.60
Purchase #3	$48.84	13.686%	$55.5242	$55.52	$55.50	$55.50
Purchase #4	$36.76	4.136%	$38.2804	$38.28	$38.30	$38.30
Purchase #5	$11.61	7.736%	$12.5081	$12.51	$12.50	$12.50
Purchase #6	$42.62	6.807%	$45.5211	$45.52	$45.50	$45.50
Purchase #7	$152.92	5.181%	$160.8428	$160.84	$160.85	$160.80
7 purchase totals =	$717.89		$771.9130	$771.91	$771.90	$771.80