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	$141.25	7.392%	$151.6912	$151.69	$151.70	$151.70
Purchase #2	$161.79	10.575%	$178.8993	$178.90	$178.90	$178.90
Purchase #3	$164.70	4.332%	$171.8348	$171.83	$171.85	$171.80
Purchase #4	$155.62	8.140%	$168.2875	$168.29	$168.30	$168.30
Purchase #5	$201.73	13.286%	$228.5318	$228.53	$228.55	$228.50
Purchase #6	$41.33	3.305%	$42.696	$42.70	$42.70	$42.70
Purchase #7	$128.80	6.750%	$137.494	$137.49	$137.50	$137.50
7 purchase totals =	$995.22		$1,079.4346	$1,079.43	$1,079.50	$1,079.40