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	$90.60	5.402%	$95.4942	$95.49	$95.50	$95.50
Purchase #2	$78.90	12.252%	$88.5668	$88.57	$88.55	$88.60
Purchase #3	$60.93	3.553%	$63.0948	$63.09	$63.10	$63.10
Purchase #4	$142.64	5.588%	$150.6107	$150.61	$150.60	$150.60
Purchase #5	$36.51	3.358%	$37.736	$37.74	$37.75	$37.70
Purchase #6	$238.44	7.186%	$255.5743	$255.57	$255.55	$255.60
Purchase #7	$19.93	13.390%	$22.5986	$22.60	$22.60	$22.60
7 purchase totals =	$667.95		$713.6754	$713.67	$713.65	$713.70