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	$97.94	13.802%	$111.4577	$111.46	$111.45	$111.50
Purchase #2	$46.53	8.465%	$50.4688	$50.47	$50.45	$50.50
Purchase #3	$36.85	9.524%	$40.3596	$40.36	$40.35	$40.40
Purchase #4	$79.36	7.178%	$85.0565	$85.06	$85.05	$85.10
Purchase #5	$247.26	3.178%	$255.1179	$255.12	$255.10	$255.10
Purchase #6	$219.80	5.207%	$231.245	$231.25	$231.25	$231.20
Purchase #7	$168.75	12.775%	$190.3078	$190.31	$190.30	$190.30
7 purchase totals =	$896.49		$964.0133	$964.03	$963.95	$964.10