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	$176.62	13.105%	$199.7661	$199.77	$199.75	$199.80
Purchase #2	$187.62	12.624%	$211.3051	$211.31	$211.30	$211.30
Purchase #3	$89.25	11.451%	$99.47	$99.47	$99.45	$99.50
Purchase #4	$224.42	3.552%	$232.3914	$232.39	$232.40	$232.40
Purchase #5	$12.79	8.483%	$13.875	$13.88	$13.90	$13.90
Purchase #6	$82.25	9.515%	$90.0761	$90.08	$90.10	$90.10
Purchase #7	$141.25	13.497%	$160.3145	$160.31	$160.30	$160.30
7 purchase totals =	$914.20		$1,007.1982	$1,007.21	$1,007.20	$1,007.30