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	$82.30	5.140%	$86.5302	$86.53	$86.55	$86.50
Purchase #2	$94.98	11.492%	$105.8951	$105.90	$105.90	$105.90
Purchase #3	$55.73	4.651%	$58.322	$58.32	$58.30	$58.30
Purchase #4	$77.93	13.699%	$88.6056	$88.61	$88.60	$88.60
Purchase #5	$102.27	10.694%	$113.2068	$113.21	$113.20	$113.20
Purchase #6	$104.47	8.679%	$113.537	$113.54	$113.55	$113.50
Purchase #7	$127.83	3.597%	$132.428	$132.43	$132.45	$132.40
7 purchase totals =	$645.51		$698.5247	$698.54	$698.55	$698.40