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	$59.25	10.758%	$65.6241	$65.62	$65.60	$65.60
Purchase #2	$104.52	4.459%	$109.1805	$109.18	$109.20	$109.20
Purchase #3	$151.25	13.324%	$171.4026	$171.40	$171.40	$171.40
Purchase #4	$36.38	8.259%	$39.3846	$39.38	$39.40	$39.40
Purchase #5	$82.48	10.575%	$91.2023	$91.20	$91.20	$91.20
Purchase #6	$38.33	4.799%	$40.1695	$40.17	$40.15	$40.20
Purchase #7	$222.69	12.423%	$250.3548	$250.35	$250.35	$250.40
7 purchase totals =	$694.90		$767.3184	$767.30	$767.30	$767.40