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	$183.59	13.574%	$208.5105	$208.51	$208.50	$208.50
Purchase #2	$155.39	6.840%	$166.0187	$166.02	$166.00	$166.00
Purchase #3	$179.79	3.464%	$186.0179	$186.02	$186.00	$186.00
Purchase #4	$37.89	12.600%	$42.6641	$42.66	$42.65	$42.70
Purchase #5	$27.30	8.162%	$29.5282	$29.53	$29.55	$29.50
Purchase #6	$136.74	8.103%	$147.82	$147.82	$147.80	$147.80
Purchase #7	$155.85	7.744%	$167.919	$167.92	$167.90	$167.90
7 purchase totals =	$876.55		$948.4784	$948.48	$948.40	$948.40