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	$92.94	8.419%	$100.7646	$100.76	$100.75	$100.80
Purchase #2	$49.81	7.132%	$53.3624	$53.36	$53.35	$53.40
Purchase #3	$159.30	8.407%	$172.6924	$172.69	$172.70	$172.70
Purchase #4	$72.48	13.817%	$82.4946	$82.49	$82.50	$82.50
Purchase #5	$93.36	10.213%	$102.8949	$102.89	$102.90	$102.90
Purchase #6	$87.93	3.312%	$90.8422	$90.84	$90.85	$90.80
Purchase #7	$243.29	7.867%	$262.4296	$262.43	$262.45	$262.40
7 purchase totals =	$799.11		$865.4807	$865.46	$865.50	$865.50