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	$44.73	7.670%	$48.1608	$48.16	$48.15	$48.20
Purchase #2	$169.31	11.517%	$188.8094	$188.81	$188.80	$188.80
Purchase #3	$189.26	5.162%	$199.0296	$199.03	$199.05	$199.00
Purchase #4	$40.34	7.830%	$43.4986	$43.50	$43.50	$43.50
Purchase #5	$144.90	6.343%	$154.091	$154.09	$154.10	$154.10
Purchase #6	$187.59	4.857%	$196.7012	$196.70	$196.70	$196.70
Purchase #7	$102.48	8.664%	$111.3589	$111.36	$111.35	$111.40
7 purchase totals =	$878.61		$941.6495	$941.65	$941.65	$941.70