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	$97.77	9.111%	$106.6778	$106.68	$106.70	$106.70
Purchase #2	$248.39	6.831%	$265.3575	$265.36	$265.35	$265.40
Purchase #3	$149.59	11.653%	$167.0217	$167.02	$167.00	$167.00
Purchase #4	$230.81	11.140%	$256.5222	$256.52	$256.50	$256.50
Purchase #5	$109.77	4.710%	$114.9402	$114.94	$114.95	$114.90
Purchase #6	$138.33	10.525%	$152.8892	$152.89	$152.90	$152.90
Purchase #7	$74.34	9.502%	$81.4038	$81.40	$81.40	$81.40
7 purchase totals =	$1,049.00		$1,144.8124	$1,144.81	$1,144.80	$1,144.80