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	$250.83	3.443%	$259.4661	$259.47	$259.45	$259.50
Purchase #2	$9.53	6.538%	$10.1531	$10.15	$10.15	$10.20
Purchase #3	$104.62	3.689%	$108.4794	$108.48	$108.50	$108.50
Purchase #4	$190.45	6.269%	$202.3893	$202.39	$202.40	$202.40
Purchase #5	$134.67	11.639%	$150.3442	$150.34	$150.35	$150.30
Purchase #6	$133.25	6.452%	$141.8473	$141.85	$141.85	$141.80
Purchase #7	$233.44	10.845%	$258.7566	$258.76	$258.75	$258.80
7 purchase totals =	$1,056.79		$1,131.4360	$1,131.44	$1,131.45	$1,131.50