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	$139.36	4.305%	$145.3594	$145.36	$145.35	$145.40
Purchase #2	$151.58	11.259%	$168.6464	$168.65	$168.65	$168.60
Purchase #3	$107.29	11.539%	$119.6702	$119.67	$119.65	$119.70
Purchase #4	$59.84	6.636%	$63.811	$63.81	$63.80	$63.80
Purchase #5	$129.40	11.548%	$144.3431	$144.34	$144.35	$144.30
Purchase #6	$191.86	9.353%	$209.8047	$209.80	$209.80	$209.80
Purchase #7	$158.84	3.554%	$164.4852	$164.49	$164.50	$164.50
7 purchase totals =	$938.17		$1,016.1200	$1,016.12	$1,016.10	$1,016.10