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	$188.52	4.805%	$197.5784	$197.58	$197.60	$197.60
Purchase #2	$201.38	7.592%	$216.6688	$216.67	$216.65	$216.70
Purchase #3	$76.96	8.450%	$83.4631	$83.46	$83.45	$83.50
Purchase #4	$143.86	5.317%	$151.509	$151.51	$151.50	$151.50
Purchase #5	$159.83	13.139%	$180.8301	$180.83	$180.85	$180.80
Purchase #6	$238.74	4.353%	$249.1324	$249.13	$249.15	$249.10
Purchase #7	$98.43	13.609%	$111.8253	$111.83	$111.85	$111.80
7 purchase totals =	$1,107.72		$1,191.0071	$1,191.01	$1,191.05	$1,191.00