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	$203.85	9.139%	$222.4799	$222.48	$222.50	$222.50
Purchase #2	$83.47	4.488%	$87.2161	$87.22	$87.20	$87.20
Purchase #3	$183.52	7.263%	$196.8491	$196.85	$196.85	$196.80
Purchase #4	$199.79	9.462%	$218.6941	$218.69	$218.70	$218.70
Purchase #5	$144.92	5.477%	$152.8573	$152.86	$152.85	$152.90
Purchase #6	$149.74	11.462%	$166.9032	$166.90	$166.90	$166.90
Purchase #7	$157.38	12.798%	$177.5215	$177.52	$177.50	$177.50
7 purchase totals =	$1,122.67		$1,222.5212	$1,222.52	$1,222.50	$1,222.50