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	$184.29	8.855%	$200.6089	$200.61	$200.60	$200.60
Purchase #2	$87.97	12.596%	$99.0507	$99.05	$99.05	$99.10
Purchase #3	$5.71	7.664%	$6.1476	$6.15	$6.15	$6.10
Purchase #4	$37.46	4.187%	$39.0285	$39.03	$39.05	$39.00
Purchase #5	$61.40	9.836%	$67.4393	$67.44	$67.45	$67.40
Purchase #6	$18.51	12.560%	$20.8349	$20.83	$20.85	$20.80
Purchase #7	$19.78	13.449%	$22.4402	$22.44	$22.45	$22.40
7 purchase totals =	$415.12		$455.5501	$455.55	$455.60	$455.40