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	$133.76	5.873%	$141.6157	$141.62	$141.60	$141.60
Purchase #2	$86.59	5.210%	$91.1013	$91.10	$91.10	$91.10
Purchase #3	$39.31	10.728%	$43.5272	$43.53	$43.55	$43.50
Purchase #4	$87.51	10.641%	$96.8219	$96.82	$96.80	$96.80
Purchase #5	$86.25	6.762%	$92.0822	$92.08	$92.10	$92.10
Purchase #6	$66.51	4.418%	$69.4484	$69.45	$69.45	$69.40
Purchase #7	$148.41	9.163%	$162.0088	$162.01	$162.00	$162.00
7 purchase totals =	$648.34		$696.6055	$696.61	$696.60	$696.50