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	$147.64	9.861%	$162.1988	$162.20	$162.20	$162.20
Purchase #2	$22.81	5.211%	$23.9986	$24.00	$24.00	$24.00
Purchase #3	$93.72	7.669%	$100.9074	$100.91	$100.90	$100.90
Purchase #4	$88.34	13.234%	$100.0309	$100.03	$100.05	$100.00
Purchase #5	$56.83	11.859%	$63.5695	$63.57	$63.55	$63.60
Purchase #6	$45.73	13.637%	$51.9662	$51.97	$51.95	$52.00
Purchase #7	$12.94	5.179%	$13.6102	$13.61	$13.60	$13.60
7 purchase totals =	$468.01		$516.2816	$516.29	$516.25	$516.30