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	$233.61	7.792%	$251.8129	$251.81	$251.80	$251.80
Purchase #2	$152.52	11.206%	$169.6114	$169.61	$169.60	$169.60
Purchase #3	$150.99	13.620%	$171.5548	$171.55	$171.55	$171.60
Purchase #4	$98.73	3.342%	$102.0296	$102.03	$102.05	$102.00
Purchase #5	$40.51	8.304%	$43.874	$43.87	$43.85	$43.90
Purchase #6	$144.92	5.461%	$152.8341	$152.83	$152.85	$152.80
Purchase #7	$155.52	6.436%	$165.5293	$165.53	$165.55	$165.50
7 purchase totals =	$976.80		$1,057.2461	$1,057.23	$1,057.25	$1,057.20