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	$217.57	4.164%	$226.6296	$226.63	$226.65	$226.60
Purchase #2	$124.56	4.376%	$130.0107	$130.01	$130.00	$130.00
Purchase #3	$99.76	5.819%	$105.565	$105.57	$105.55	$105.60
Purchase #4	$18.92	8.440%	$20.5168	$20.52	$20.50	$20.50
Purchase #5	$86.27	5.165%	$90.7258	$90.73	$90.75	$90.70
Purchase #6	$126.52	8.545%	$137.3311	$137.33	$137.35	$137.30
Purchase #7	$176.62	9.743%	$193.8281	$193.83	$193.85	$193.80
7 purchase totals =	$850.22		$904.6071	$904.62	$904.65	$904.50