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	$159.27	4.843%	$166.9834	$166.98	$167.00	$167.00
Purchase #2	$89.65	6.202%	$95.2101	$95.21	$95.20	$95.20
Purchase #3	$156.41	7.637%	$168.355	$168.36	$168.35	$168.40
Purchase #4	$76.30	3.375%	$78.8751	$78.88	$78.90	$78.90
Purchase #5	$76.39	12.148%	$85.6699	$85.67	$85.65	$85.70
Purchase #6	$169.67	12.535%	$190.9381	$190.94	$190.95	$190.90
Purchase #7	$236.96	8.130%	$256.2248	$256.22	$256.20	$256.20
7 purchase totals =	$964.65		$1,042.2564	$1,042.26	$1,042.25	$1,042.30