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	$113.75	13.618%	$129.2405	$129.24	$129.25	$129.20
Purchase #2	$201.69	10.323%	$222.5105	$222.51	$222.50	$222.50
Purchase #3	$132.63	8.708%	$144.1794	$144.18	$144.20	$144.20
Purchase #4	$98.72	5.385%	$104.0361	$104.04	$104.05	$104.00
Purchase #5	$228.96	6.414%	$243.6455	$243.65	$243.65	$243.60
Purchase #6	$189.86	13.449%	$215.3943	$215.39	$215.40	$215.40
Purchase #7	$144.58	13.855%	$164.6116	$164.61	$164.60	$164.60
7 purchase totals =	$1,110.19		$1,223.6179	$1,223.62	$1,223.65	$1,223.50