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	$154.34	11.313%	$171.8005	$171.80	$171.80	$171.80
Purchase #2	$128.85	10.121%	$141.8909	$141.89	$141.90	$141.90
Purchase #3	$11.97	4.745%	$12.538	$12.54	$12.55	$12.50
Purchase #4	$104.51	3.371%	$108.033	$108.03	$108.05	$108.00
Purchase #5	$40.69	11.819%	$45.4992	$45.50	$45.50	$45.50
Purchase #6	$16.53	10.109%	$18.201	$18.20	$18.20	$18.20
Purchase #7	$215.57	6.152%	$228.8319	$228.83	$228.85	$228.80
7 purchase totals =	$672.46		$726.7945	$726.79	$726.85	$726.70