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	$85.28	11.668%	$95.2305	$95.23	$95.25	$95.20
Purchase #2	$81.35	10.651%	$90.0146	$90.01	$90.00	$90.00
Purchase #3	$18.70	9.790%	$20.5307	$20.53	$20.55	$20.50
Purchase #4	$69.36	11.598%	$77.4044	$77.40	$77.40	$77.40
Purchase #5	$148.51	8.120%	$160.569	$160.57	$160.55	$160.60
Purchase #6	$94.97	9.650%	$104.1346	$104.13	$104.15	$104.10
Purchase #7	$152.32	12.640%	$171.5732	$171.57	$171.55	$171.60
7 purchase totals =	$650.49		$719.4570	$719.44	$719.45	$719.40