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	$62.64	7.846%	$67.5547	$67.55	$67.55	$67.60
Purchase #2	$14.35	11.659%	$16.0231	$16.02	$16.00	$16.00
Purchase #3	$100.54	9.182%	$109.7716	$109.77	$109.75	$109.80
Purchase #4	$25.55	10.190%	$28.1535	$28.15	$28.15	$28.20
Purchase #5	$138.63	9.219%	$151.4103	$151.41	$151.40	$151.40
Purchase #6	$240.64	13.389%	$272.8593	$272.86	$272.85	$272.90
Purchase #7	$84.46	6.613%	$90.0453	$90.05	$90.05	$90.00
7 purchase totals =	$666.81		$735.8178	$735.81	$735.75	$735.90