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	$76.25	6.601%	$81.2833	$81.28	$81.30	$81.30
Purchase #2	$246.39	6.538%	$262.499	$262.50	$262.50	$262.50
Purchase #3	$14.59	4.408%	$15.2331	$15.23	$15.25	$15.20
Purchase #4	$137.61	7.428%	$147.8317	$147.83	$147.85	$147.80
Purchase #5	$119.59	4.422%	$124.8783	$124.88	$124.90	$124.90
Purchase #6	$157.98	8.602%	$171.5694	$171.57	$171.55	$171.60
Purchase #7	$233.42	13.378%	$264.6469	$264.65	$264.65	$264.60
7 purchase totals =	$985.83		$1,067.9417	$1,067.94	$1,068.00	$1,067.90