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	$166.72	3.830%	$173.1054	$173.11	$173.10	$173.10
Purchase #2	$78.50	3.831%	$81.5073	$81.51	$81.50	$81.50
Purchase #3	$39.56	11.439%	$44.0853	$44.09	$44.10	$44.10
Purchase #4	$166.92	13.390%	$189.2706	$189.27	$189.25	$189.30
Purchase #5	$39.54	5.616%	$41.7606	$41.76	$41.75	$41.80
Purchase #6	$216.85	13.136%	$245.3354	$245.34	$245.35	$245.30
Purchase #7	$172.40	11.289%	$191.8622	$191.86	$191.85	$191.90
7 purchase totals =	$880.49		$966.9268	$966.94	$966.90	$967.00