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	$59.68	13.217%	$67.5679	$67.57	$67.55	$67.60
Purchase #2	$34.73	13.548%	$39.4352	$39.44	$39.45	$39.40
Purchase #3	$6.47	13.757%	$7.3601	$7.36	$7.35	$7.40
Purchase #4	$140.34	8.296%	$151.9826	$151.98	$152.00	$152.00
Purchase #5	$20.55	8.770%	$22.3522	$22.35	$22.35	$22.40
Purchase #6	$99.78	5.250%	$105.0185	$105.02	$105.00	$105.00
Purchase #7	$11.30	9.536%	$12.3776	$12.38	$12.40	$12.40
7 purchase totals =	$372.85		$406.0941	$406.10	$406.10	$406.20