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	$59.94	9.401%	$65.575	$65.58	$65.60	$65.60
Purchase #2	$90.89	9.166%	$99.221	$99.22	$99.20	$99.20
Purchase #3	$239.46	8.144%	$258.9616	$258.96	$258.95	$259.00
Purchase #4	$103.62	5.274%	$109.0849	$109.08	$109.10	$109.10
Purchase #5	$194.80	11.624%	$217.4436	$217.44	$217.45	$217.40
Purchase #6	$31.60	7.304%	$33.9081	$33.91	$33.90	$33.90
Purchase #7	$66.55	9.164%	$72.6486	$72.65	$72.65	$72.60
7 purchase totals =	$786.86		$856.8428	$856.84	$856.85	$856.80