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	$70.79	6.609%	$75.4685	$75.47	$75.45	$75.50
Purchase #2	$121.37	4.165%	$126.4251	$126.43	$126.45	$126.40
Purchase #3	$57.85	13.405%	$65.6048	$65.60	$65.60	$65.60
Purchase #4	$143.27	5.334%	$150.912	$150.91	$150.90	$150.90
Purchase #5	$56.82	13.692%	$64.5998	$64.60	$64.60	$64.60
Purchase #6	$188.61	9.693%	$206.892	$206.89	$206.90	$206.90
Purchase #7	$90.47	11.188%	$100.5918	$100.59	$100.60	$100.60
7 purchase totals =	$729.18		$790.4940	$790.49	$790.50	$790.50