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	$162.85	12.103%	$182.5597	$182.56	$182.55	$182.60
Purchase #2	$79.46	12.200%	$89.1541	$89.15	$89.15	$89.20
Purchase #3	$73.41	8.536%	$79.6763	$79.68	$79.70	$79.70
Purchase #4	$171.93	7.790%	$185.3233	$185.32	$185.30	$185.30
Purchase #5	$216.89	13.779%	$246.7753	$246.78	$246.80	$246.80
Purchase #6	$61.28	8.445%	$66.4551	$66.46	$66.45	$66.50
Purchase #7	$140.91	9.277%	$153.9822	$153.98	$154.00	$154.00
7 purchase totals =	$906.73		$1,003.9260	$1,003.93	$1,003.95	$1,004.10