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	$58.96	6.402%	$62.7346	$62.73	$62.75	$62.70
Purchase #2	$228.28	12.502%	$256.8196	$256.82	$256.80	$256.80
Purchase #3	$86.67	13.604%	$98.4606	$98.46	$98.45	$98.50
Purchase #4	$158.98	8.562%	$172.5919	$172.59	$172.60	$172.60
Purchase #5	$214.55	10.822%	$237.7686	$237.77	$237.75	$237.80
Purchase #6	$112.99	12.665%	$127.3002	$127.30	$127.30	$127.30
Purchase #7	$180.55	5.317%	$190.1498	$190.15	$190.15	$190.10
7 purchase totals =	$1,040.98		$1,145.8253	$1,145.82	$1,145.80	$1,145.80