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	$59.85	3.274%	$61.8095	$61.81	$61.80	$61.80
Purchase #2	$78.89	3.151%	$81.3758	$81.38	$81.40	$81.40
Purchase #3	$39.34	10.746%	$43.5675	$43.57	$43.55	$43.60
Purchase #4	$212.26	11.488%	$236.6444	$236.64	$236.65	$236.60
Purchase #5	$16.72	13.482%	$18.9742	$18.97	$18.95	$19.00
Purchase #6	$199.48	11.357%	$222.1349	$222.13	$222.15	$222.10
Purchase #7	$75.73	5.790%	$80.1148	$80.11	$80.10	$80.10
7 purchase totals =	$682.27		$744.6211	$744.61	$744.60	$744.60