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	$165.59	10.116%	$182.3411	$182.34	$182.35	$182.30
Purchase #2	$168.41	13.570%	$191.2632	$191.26	$191.25	$191.30
Purchase #3	$140.71	9.526%	$154.114	$154.11	$154.10	$154.10
Purchase #4	$239.92	13.608%	$272.5683	$272.57	$272.55	$272.60
Purchase #5	$12.54	12.455%	$14.1019	$14.10	$14.10	$14.10
Purchase #6	$31.82	12.754%	$35.8783	$35.88	$35.90	$35.90
Purchase #7	$61.80	5.590%	$65.2546	$65.25	$65.25	$65.30
7 purchase totals =	$820.79		$915.5214	$915.51	$915.50	$915.60