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	$166.49	3.223%	$171.856	$171.86	$171.85	$171.90
Purchase #2	$25.47	6.770%	$27.1943	$27.19	$27.20	$27.20
Purchase #3	$168.61	6.855%	$180.1682	$180.17	$180.15	$180.20
Purchase #4	$235.56	3.562%	$243.9506	$243.95	$243.95	$244.00
Purchase #5	$147.85	13.643%	$168.0212	$168.02	$168.00	$168.00
Purchase #6	$36.81	9.659%	$40.3655	$40.37	$40.35	$40.40
Purchase #7	$204.85	3.431%	$211.8784	$211.88	$211.90	$211.90
7 purchase totals =	$985.64		$1,043.4342	$1,043.44	$1,043.40	$1,043.60