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	$169.83	9.482%	$185.9333	$185.93	$185.95	$185.90
Purchase #2	$107.87	9.787%	$118.4272	$118.43	$118.45	$118.40
Purchase #3	$41.68	7.856%	$44.9544	$44.95	$44.95	$45.00
Purchase #4	$127.52	11.141%	$141.727	$141.73	$141.75	$141.70
Purchase #5	$197.39	10.158%	$217.4409	$217.44	$217.45	$217.40
Purchase #6	$79.37	5.297%	$83.5742	$83.57	$83.55	$83.60
Purchase #7	$220.48	13.760%	$250.818	$250.82	$250.80	$250.80
7 purchase totals =	$944.14		$1,042.8750	$1,042.87	$1,042.90	$1,042.80