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	$192.47	7.279%	$206.4799	$206.48	$206.50	$206.50
Purchase #2	$31.85	8.423%	$34.5327	$34.53	$34.55	$34.50
Purchase #3	$20.25	5.538%	$21.3714	$21.37	$21.35	$21.40
Purchase #4	$81.56	9.132%	$89.0081	$89.01	$89.00	$89.00
Purchase #5	$56.51	6.428%	$60.1425	$60.14	$60.15	$60.10
Purchase #6	$117.28	12.678%	$132.1488	$132.15	$132.15	$132.10
Purchase #7	$46.97	12.235%	$52.7168	$52.72	$52.70	$52.70
7 purchase totals =	$546.89		$596.4002	$596.40	$596.40	$596.30