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	$44.94	9.393%	$49.1612	$49.16	$49.15	$49.20
Purchase #2	$140.84	12.698%	$158.7239	$158.72	$158.70	$158.70
Purchase #3	$74.87	13.677%	$85.11	$85.11	$85.10	$85.10
Purchase #4	$249.94	7.169%	$267.8582	$267.86	$267.85	$267.90
Purchase #5	$204.55	5.768%	$216.3484	$216.35	$216.35	$216.30
Purchase #6	$73.78	6.743%	$78.755	$78.76	$78.75	$78.80
Purchase #7	$93.84	7.167%	$100.5655	$100.57	$100.55	$100.60
7 purchase totals =	$882.76		$956.5222	$956.53	$956.45	$956.60