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	$102.38	7.399%	$109.9551	$109.96	$109.95	$110.00
Purchase #2	$54.39	10.380%	$60.0357	$60.04	$60.05	$60.00
Purchase #3	$28.69	11.439%	$31.9718	$31.97	$31.95	$32.00
Purchase #4	$24.57	11.738%	$27.454	$27.45	$27.45	$27.50
Purchase #5	$223.71	13.653%	$254.2531	$254.25	$254.25	$254.30
Purchase #6	$43.27	11.307%	$48.1625	$48.16	$48.15	$48.20
Purchase #7	$29.49	7.217%	$31.6183	$31.62	$31.60	$31.60
7 purchase totals =	$506.50		$563.4505	$563.45	$563.40	$563.60