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	$232.47	6.604%	$247.8223	$247.82	$247.80	$247.80
Purchase #2	$86.81	4.516%	$90.7303	$90.73	$90.75	$90.70
Purchase #3	$131.43	11.400%	$146.413	$146.41	$146.40	$146.40
Purchase #4	$228.83	5.669%	$241.8024	$241.80	$241.80	$241.80
Purchase #5	$102.40	10.304%	$112.9513	$112.95	$112.95	$113.00
Purchase #6	$188.31	6.525%	$200.5972	$200.60	$200.60	$200.60
Purchase #7	$91.56	10.720%	$101.3752	$101.38	$101.40	$101.40
7 purchase totals =	$1,061.81		$1,141.6917	$1,141.69	$1,141.70	$1,141.70