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	$186.48	5.431%	$196.6077	$196.61	$196.60	$196.60
Purchase #2	$208.60	13.291%	$236.325	$236.33	$236.35	$236.30
Purchase #3	$29.95	5.849%	$31.7018	$31.70	$31.70	$31.70
Purchase #4	$233.88	5.565%	$246.8954	$246.90	$246.90	$246.90
Purchase #5	$40.86	12.495%	$45.9655	$45.97	$45.95	$46.00
Purchase #6	$34.91	9.792%	$38.3284	$38.33	$38.35	$38.30
Purchase #7	$67.87	4.778%	$71.1128	$71.11	$71.10	$71.10
7 purchase totals =	$802.55		$866.9366	$866.95	$866.95	$866.90