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	$97.57	3.472%	$100.9576	$100.96	$100.95	$101.00
Purchase #2	$212.49	4.846%	$222.7873	$222.79	$222.80	$222.80
Purchase #3	$157.93	11.772%	$176.5215	$176.52	$176.50	$176.50
Purchase #4	$61.69	5.379%	$65.0083	$65.01	$65.00	$65.00
Purchase #5	$47.60	11.321%	$52.9888	$52.99	$53.00	$53.00
Purchase #6	$71.94	11.519%	$80.2268	$80.23	$80.25	$80.20
Purchase #7	$64.88	10.228%	$71.5159	$71.52	$71.50	$71.50
7 purchase totals =	$714.10		$770.0062	$770.02	$770.00	$770.00