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	$173.91	6.753%	$185.6541	$185.65	$185.65	$185.70
Purchase #2	$75.63	9.676%	$82.948	$82.95	$82.95	$82.90
Purchase #3	$29.26	4.285%	$30.5138	$30.51	$30.50	$30.50
Purchase #4	$38.38	9.486%	$42.0207	$42.02	$42.00	$42.00
Purchase #5	$249.47	10.174%	$274.8511	$274.85	$274.85	$274.90
Purchase #6	$150.29	7.478%	$161.5287	$161.53	$161.55	$161.50
Purchase #7	$94.89	11.500%	$105.8024	$105.80	$105.80	$105.80
7 purchase totals =	$811.83		$883.3188	$883.31	$883.30	$883.30