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	$56.69	11.759%	$63.3562	$63.36	$63.35	$63.40
Purchase #2	$248.83	10.158%	$274.1062	$274.11	$274.10	$274.10
Purchase #3	$39.90	8.630%	$43.3434	$43.34	$43.35	$43.30
Purchase #4	$50.68	5.673%	$53.5551	$53.56	$53.55	$53.60
Purchase #5	$200.89	11.196%	$223.3816	$223.38	$223.40	$223.40
Purchase #6	$143.95	6.642%	$153.5112	$153.51	$153.50	$153.50
Purchase #7	$54.93	10.842%	$60.8855	$60.89	$60.90	$60.90
7 purchase totals =	$795.87		$872.1392	$872.15	$872.15	$872.20