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	$107.94	9.420%	$118.1079	$118.11	$118.10	$118.10
Purchase #2	$131.38	13.874%	$149.6077	$149.61	$149.60	$149.60
Purchase #3	$52.69	13.594%	$59.8527	$59.85	$59.85	$59.90
Purchase #4	$179.96	9.380%	$196.8402	$196.84	$196.85	$196.80
Purchase #5	$175.82	10.273%	$193.882	$193.88	$193.90	$193.90
Purchase #6	$46.60	12.425%	$52.3901	$52.39	$52.40	$52.40
Purchase #7	$195.31	9.863%	$214.5734	$214.57	$214.55	$214.60
7 purchase totals =	$889.70		$985.2540	$985.25	$985.25	$985.30