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	$162.72	6.126%	$172.6882	$172.69	$172.70	$172.70
Purchase #2	$77.67	6.528%	$82.7403	$82.74	$82.75	$82.70
Purchase #3	$178.90	11.112%	$198.7794	$198.78	$198.80	$198.80
Purchase #4	$189.94	8.824%	$206.7003	$206.70	$206.70	$206.70
Purchase #5	$232.88	10.185%	$256.5988	$256.60	$256.60	$256.60
Purchase #6	$16.29	6.131%	$17.2887	$17.29	$17.30	$17.30
Purchase #7	$78.72	8.437%	$85.3616	$85.36	$85.35	$85.40
7 purchase totals =	$937.12		$1,020.1573	$1,020.16	$1,020.20	$1,020.20