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	$123.95	13.574%	$140.775	$140.78	$140.80	$140.80
Purchase #2	$214.59	12.851%	$242.167	$242.17	$242.15	$242.20
Purchase #3	$75.80	13.228%	$85.8268	$85.83	$85.85	$85.80
Purchase #4	$110.69	5.665%	$116.9606	$116.96	$116.95	$117.00
Purchase #5	$62.56	7.152%	$67.0343	$67.03	$67.05	$67.00
Purchase #6	$25.35	11.586%	$28.2871	$28.29	$28.30	$28.30
Purchase #7	$81.25	6.448%	$86.489	$86.49	$86.50	$86.50
7 purchase totals =	$694.19		$767.5398	$767.55	$767.60	$767.60