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	$115.27	12.530%	$129.7133	$129.71	$129.70	$129.70
Purchase #2	$125.59	11.511%	$140.0467	$140.05	$140.05	$140.00
Purchase #3	$208.58	3.746%	$216.3934	$216.39	$216.40	$216.40
Purchase #4	$192.83	9.672%	$211.4805	$211.48	$211.50	$211.50
Purchase #5	$71.37	10.538%	$78.891	$78.89	$78.90	$78.90
Purchase #6	$240.32	6.296%	$255.4505	$255.45	$255.45	$255.50
Purchase #7	$107.99	6.324%	$114.8193	$114.82	$114.80	$114.80
7 purchase totals =	$1,061.95		$1,146.7947	$1,146.79	$1,146.80	$1,146.80