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	$115.56	11.849%	$129.2527	$129.25	$129.25	$129.30
Purchase #2	$26.99	12.439%	$30.3473	$30.35	$30.35	$30.30
Purchase #3	$241.38	8.338%	$261.5063	$261.51	$261.50	$261.50
Purchase #4	$158.69	8.838%	$172.715	$172.72	$172.70	$172.70
Purchase #5	$169.60	9.360%	$185.4746	$185.47	$185.45	$185.50
Purchase #6	$199.98	11.457%	$222.8917	$222.89	$222.90	$222.90
Purchase #7	$50.97	13.616%	$57.9101	$57.91	$57.90	$57.90
7 purchase totals =	$963.17		$1,060.0977	$1,060.10	$1,060.05	$1,060.10