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	$162.36	13.568%	$184.389	$184.39	$184.40	$184.40
Purchase #2	$146.52	3.213%	$151.2277	$151.23	$151.25	$151.20
Purchase #3	$106.74	8.534%	$115.8492	$115.85	$115.85	$115.80
Purchase #4	$76.93	8.185%	$83.2267	$83.23	$83.25	$83.20
Purchase #5	$225.55	12.665%	$254.1159	$254.12	$254.10	$254.10
Purchase #6	$69.26	13.824%	$78.8345	$78.83	$78.85	$78.80
Purchase #7	$164.74	9.230%	$179.9455	$179.95	$179.95	$179.90
7 purchase totals =	$952.10		$1,047.5885	$1,047.60	$1,047.65	$1,047.40