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	$183.75	3.217%	$189.6612	$189.66	$189.65	$189.70
Purchase #2	$185.27	13.120%	$209.5774	$209.58	$209.60	$209.60
Purchase #3	$197.63	7.236%	$211.9305	$211.93	$211.95	$211.90
Purchase #4	$158.85	7.282%	$170.4175	$170.42	$170.40	$170.40
Purchase #5	$170.50	7.265%	$182.8868	$182.89	$182.90	$182.90
Purchase #6	$72.83	7.107%	$78.006	$78.01	$78.00	$78.00
Purchase #7	$191.27	10.536%	$211.4222	$211.42	$211.40	$211.40
7 purchase totals =	$1,160.10		$1,253.9016	$1,253.91	$1,253.90	$1,253.90