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	$59.83	12.516%	$67.3183	$67.32	$67.30	$67.30
Purchase #2	$7.25	9.104%	$7.91	$7.91	$7.90	$7.90
Purchase #3	$241.83	11.795%	$270.3538	$270.35	$270.35	$270.40
Purchase #4	$207.95	9.168%	$227.0149	$227.01	$227.00	$227.00
Purchase #5	$54.39	5.218%	$57.2281	$57.23	$57.25	$57.20
Purchase #6	$143.89	10.176%	$158.5322	$158.53	$158.55	$158.50
Purchase #7	$18.62	7.313%	$19.9817	$19.98	$20.00	$20.00
7 purchase totals =	$733.76		$808.3390	$808.33	$808.35	$808.30