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	$149.70	11.115%	$166.3392	$166.34	$166.35	$166.30
Purchase #2	$36.49	11.792%	$40.7929	$40.79	$40.80	$40.80
Purchase #3	$150.50	8.311%	$163.0081	$163.01	$163.00	$163.00
Purchase #4	$72.90	12.636%	$82.1116	$82.11	$82.10	$82.10
Purchase #5	$203.82	9.104%	$222.3758	$222.38	$222.40	$222.40
Purchase #6	$43.52	5.256%	$45.8074	$45.81	$45.80	$45.80
Purchase #7	$82.25	11.418%	$91.6413	$91.64	$91.65	$91.60
7 purchase totals =	$739.18		$812.0763	$812.08	$812.10	$812.00