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	$6.85	8.789%	$7.452	$7.45	$7.45	$7.50
Purchase #2	$40.71	8.355%	$44.1113	$44.11	$44.10	$44.10
Purchase #3	$69.96	11.417%	$77.9473	$77.95	$77.95	$77.90
Purchase #4	$10.86	10.689%	$12.0208	$12.02	$12.00	$12.00
Purchase #5	$57.49	3.197%	$59.328	$59.33	$59.35	$59.30
Purchase #6	$126.49	5.339%	$133.2433	$133.24	$133.25	$133.20
Purchase #7	$6.66	11.674%	$7.4375	$7.44	$7.45	$7.40
7 purchase totals =	$319.02		$341.5402	$341.54	$341.55	$341.40