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	$167.67	11.293%	$186.605	$186.61	$186.60	$186.60
Purchase #2	$39.70	3.150%	$40.9506	$40.95	$40.95	$41.00
Purchase #3	$210.77	6.274%	$223.9937	$223.99	$224.00	$224.00
Purchase #4	$183.89	13.277%	$208.3051	$208.31	$208.30	$208.30
Purchase #5	$72.37	7.817%	$78.0272	$78.03	$78.05	$78.00
Purchase #6	$43.56	8.256%	$47.1563	$47.16	$47.15	$47.20
Purchase #7	$148.50	10.760%	$164.4786	$164.48	$164.50	$164.50
7 purchase totals =	$866.46		$949.5165	$949.53	$949.55	$949.60