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	$93.52	7.758%	$100.7753	$100.78	$100.80	$100.80
Purchase #2	$12.46	5.180%	$13.1054	$13.11	$13.10	$13.10
Purchase #3	$147.58	11.732%	$164.8941	$164.89	$164.90	$164.90
Purchase #4	$168.74	11.449%	$188.059	$188.06	$188.05	$188.10
Purchase #5	$160.99	5.593%	$169.9942	$169.99	$170.00	$170.00
Purchase #6	$39.53	3.286%	$40.829	$40.83	$40.85	$40.80
Purchase #7	$62.66	8.236%	$67.8207	$67.82	$67.80	$67.80
7 purchase totals =	$685.48		$745.4777	$745.48	$745.50	$745.50