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	$75.83	9.450%	$82.9959	$83.00	$83.00	$83.00
Purchase #2	$59.87	8.219%	$64.7907	$64.79	$64.80	$64.80
Purchase #3	$126.78	3.151%	$130.7748	$130.77	$130.75	$130.80
Purchase #4	$52.45	6.184%	$55.6935	$55.69	$55.70	$55.70
Purchase #5	$195.30	5.170%	$205.397	$205.40	$205.40	$205.40
Purchase #6	$83.88	6.651%	$89.4589	$89.46	$89.45	$89.50
Purchase #7	$230.35	12.211%	$258.478	$258.48	$258.50	$258.50
7 purchase totals =	$824.46		$887.5888	$887.59	$887.60	$887.70