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	$52.50	6.439%	$55.8805	$55.88	$55.90	$55.90
Purchase #2	$152.63	3.343%	$157.7324	$157.73	$157.75	$157.70
Purchase #3	$179.61	10.676%	$198.7852	$198.79	$198.80	$198.80
Purchase #4	$87.46	13.724%	$99.463	$99.46	$99.45	$99.50
Purchase #5	$68.91	12.484%	$77.5127	$77.51	$77.50	$77.50
Purchase #6	$73.87	10.184%	$81.3929	$81.39	$81.40	$81.40
Purchase #7	$56.87	7.650%	$61.2206	$61.22	$61.20	$61.20
7 purchase totals =	$671.85		$731.9873	$731.98	$732.00	$732.00