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	$81.37	12.812%	$91.7951	$91.80	$91.80	$91.80
Purchase #2	$123.81	5.820%	$131.0157	$131.02	$131.00	$131.00
Purchase #3	$125.95	4.329%	$131.4024	$131.40	$131.40	$131.40
Purchase #4	$55.35	7.368%	$59.4282	$59.43	$59.45	$59.40
Purchase #5	$154.27	5.378%	$162.5666	$162.57	$162.55	$162.60
Purchase #6	$94.58	12.512%	$106.4138	$106.41	$106.40	$106.40
Purchase #7	$45.30	9.544%	$49.6234	$49.62	$49.60	$49.60
7 purchase totals =	$680.63		$732.2452	$732.25	$732.20	$732.20