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	$92.50	4.265%	$96.4451	$96.45	$96.45	$96.40
Purchase #2	$37.51	4.712%	$39.2775	$39.28	$39.30	$39.30
Purchase #3	$58.61	8.341%	$63.4987	$63.50	$63.50	$63.50
Purchase #4	$193.88	7.246%	$207.9285	$207.93	$207.95	$207.90
Purchase #5	$143.63	10.458%	$158.6508	$158.65	$158.65	$158.70
Purchase #6	$43.92	3.150%	$45.3035	$45.30	$45.30	$45.30
Purchase #7	$188.62	4.316%	$196.7608	$196.76	$196.75	$196.80
7 purchase totals =	$758.67		$807.8649	$807.87	$807.90	$807.90