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	$130.60	5.350%	$137.5871	$137.59	$137.60	$137.60
Purchase #2	$184.86	13.213%	$209.2856	$209.29	$209.30	$209.30
Purchase #3	$179.61	13.206%	$203.3293	$203.33	$203.35	$203.30
Purchase #4	$116.42	8.457%	$126.2656	$126.27	$126.25	$126.30
Purchase #5	$90.61	11.269%	$100.8208	$100.82	$100.80	$100.80
Purchase #6	$111.41	12.226%	$125.031	$125.03	$125.05	$125.00
Purchase #7	$118.71	8.298%	$128.5606	$128.56	$128.55	$128.60
7 purchase totals =	$932.22		$1,030.8800	$1,030.89	$1,030.90	$1,030.90