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	$233.98	7.308%	$251.0793	$251.08	$251.10	$251.10
Purchase #2	$168.45	13.137%	$190.5793	$190.58	$190.60	$190.60
Purchase #3	$182.45	5.169%	$191.8808	$191.88	$191.90	$191.90
Purchase #4	$30.54	6.731%	$32.5956	$32.60	$32.60	$32.60
Purchase #5	$69.38	6.704%	$74.0312	$74.03	$74.05	$74.00
Purchase #6	$192.53	13.500%	$218.5216	$218.52	$218.50	$218.50
Purchase #7	$67.52	13.246%	$76.4637	$76.46	$76.45	$76.50
7 purchase totals =	$944.85		$1,035.1515	$1,035.15	$1,035.20	$1,035.20