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	$143.65	5.224%	$151.1543	$151.15	$151.15	$151.20
Purchase #2	$173.50	3.544%	$179.6488	$179.65	$179.65	$179.60
Purchase #3	$95.85	8.673%	$104.1631	$104.16	$104.15	$104.20
Purchase #4	$98.25	4.708%	$102.8756	$102.88	$102.90	$102.90
Purchase #5	$109.61	4.742%	$114.8077	$114.81	$114.80	$114.80
Purchase #6	$104.69	11.627%	$116.8623	$116.86	$116.85	$116.90
Purchase #7	$206.77	3.538%	$214.0855	$214.09	$214.10	$214.10
7 purchase totals =	$932.32		$983.5973	$983.60	$983.60	$983.70