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	$124.45	5.480%	$131.2699	$131.27	$131.25	$131.30
Purchase #2	$151.99	3.403%	$157.1622	$157.16	$157.15	$157.20
Purchase #3	$83.70	6.304%	$88.9764	$88.98	$89.00	$89.00
Purchase #4	$175.73	11.855%	$196.5628	$196.56	$196.55	$196.60
Purchase #5	$163.93	5.291%	$172.6035	$172.60	$172.60	$172.60
Purchase #6	$224.80	3.140%	$231.8587	$231.86	$231.85	$231.90
Purchase #7	$80.63	11.600%	$89.9831	$89.98	$90.00	$90.00
7 purchase totals =	$1,005.23		$1,068.4166	$1,068.41	$1,068.40	$1,068.60