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	$174.72	12.497%	$196.5548	$196.55	$196.55	$196.60
Purchase #2	$30.29	5.300%	$31.8954	$31.90	$31.90	$31.90
Purchase #3	$131.59	13.752%	$149.6863	$149.69	$149.70	$149.70
Purchase #4	$147.69	4.834%	$154.8293	$154.83	$154.85	$154.80
Purchase #5	$125.62	13.417%	$142.4744	$142.47	$142.45	$142.50
Purchase #6	$18.91	13.385%	$21.4411	$21.44	$21.45	$21.40
Purchase #7	$83.64	10.673%	$92.5669	$92.57	$92.55	$92.60
7 purchase totals =	$712.46		$789.4482	$789.45	$789.45	$789.50