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	$122.39	9.558%	$134.088	$134.09	$134.10	$134.10
Purchase #2	$140.93	8.199%	$152.4849	$152.48	$152.50	$152.50
Purchase #3	$231.80	11.364%	$258.1418	$258.14	$258.15	$258.10
Purchase #4	$93.79	6.358%	$99.7532	$99.75	$99.75	$99.80
Purchase #5	$166.96	13.492%	$189.4862	$189.49	$189.50	$189.50
Purchase #6	$42.45	3.473%	$43.9243	$43.92	$43.90	$43.90
Purchase #7	$52.41	4.188%	$54.6049	$54.60	$54.60	$54.60
7 purchase totals =	$850.73		$932.4833	$932.47	$932.50	$932.50