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	$59.41	3.184%	$61.3016	$61.30	$61.30	$61.30
Purchase #2	$104.38	11.145%	$116.0132	$116.01	$116.00	$116.00
Purchase #3	$75.76	8.782%	$82.4132	$82.41	$82.40	$82.40
Purchase #4	$41.97	12.372%	$47.1625	$47.16	$47.15	$47.20
Purchase #5	$124.45	13.575%	$141.3441	$141.34	$141.35	$141.30
Purchase #6	$141.38	4.176%	$147.284	$147.28	$147.30	$147.30
Purchase #7	$118.53	4.825%	$124.2491	$124.25	$124.25	$124.20
7 purchase totals =	$665.88		$719.7677	$719.75	$719.75	$719.70