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	$134.44	6.116%	$142.6624	$142.66	$142.65	$142.70
Purchase #2	$190.56	3.370%	$196.9819	$196.98	$197.00	$197.00
Purchase #3	$165.49	4.504%	$172.9437	$172.94	$172.95	$172.90
Purchase #4	$42.53	7.305%	$45.6368	$45.64	$45.65	$45.60
Purchase #5	$211.51	5.159%	$222.4218	$222.42	$222.40	$222.40
Purchase #6	$208.56	13.106%	$235.8939	$235.89	$235.90	$235.90
Purchase #7	$85.94	8.790%	$93.4941	$93.49	$93.50	$93.50
7 purchase totals =	$1,039.03		$1,110.0346	$1,110.02	$1,110.05	$1,110.00