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	$66.98	8.570%	$72.7202	$72.72	$72.70	$72.70
Purchase #2	$72.55	4.764%	$76.0063	$76.01	$76.00	$76.00
Purchase #3	$170.35	5.480%	$179.6852	$179.69	$179.70	$179.70
Purchase #4	$39.57	10.311%	$43.6501	$43.65	$43.65	$43.70
Purchase #5	$214.92	12.867%	$242.5738	$242.57	$242.55	$242.60
Purchase #6	$67.71	7.343%	$72.6819	$72.68	$72.70	$72.70
Purchase #7	$157.83	3.213%	$162.9011	$162.90	$162.90	$162.90
7 purchase totals =	$789.91		$850.2186	$850.22	$850.20	$850.30