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	$82.32	3.834%	$85.4761	$85.48	$85.50	$85.50
Purchase #2	$137.43	10.274%	$151.5496	$151.55	$151.55	$151.50
Purchase #3	$101.71	3.661%	$105.4336	$105.43	$105.45	$105.40
Purchase #4	$132.62	8.541%	$143.9471	$143.95	$143.95	$143.90
Purchase #5	$110.59	5.158%	$116.2942	$116.29	$116.30	$116.30
Purchase #6	$29.67	4.478%	$30.9986	$31.00	$31.00	$31.00
Purchase #7	$61.93	8.615%	$67.2653	$67.27	$67.25	$67.30
7 purchase totals =	$656.27		$700.9645	$700.97	$701.00	$700.90