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	$81.97	8.505%	$88.9415	$88.94	$88.95	$88.90
Purchase #2	$165.79	3.489%	$171.5744	$171.57	$171.55	$171.60
Purchase #3	$107.48	3.677%	$111.432	$111.43	$111.45	$111.40
Purchase #4	$129.54	10.290%	$142.8697	$142.87	$142.85	$142.90
Purchase #5	$17.57	6.111%	$18.6437	$18.64	$18.65	$18.60
Purchase #6	$119.33	4.401%	$124.5817	$124.58	$124.60	$124.60
Purchase #7	$52.41	13.256%	$59.3575	$59.36	$59.35	$59.40
7 purchase totals =	$674.09		$717.4005	$717.39	$717.40	$717.40