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	$73.25	12.668%	$82.5293	$82.53	$82.55	$82.50
Purchase #2	$150.40	7.158%	$161.1656	$161.17	$161.15	$161.20
Purchase #3	$76.88	12.552%	$86.53	$86.53	$86.55	$86.50
Purchase #4	$105.57	4.115%	$109.9142	$109.91	$109.90	$109.90
Purchase #5	$118.92	12.732%	$134.0609	$134.06	$134.05	$134.10
Purchase #6	$209.49	3.838%	$217.5302	$217.53	$217.55	$217.50
Purchase #7	$29.34	13.609%	$33.3329	$33.33	$33.35	$33.30
7 purchase totals =	$763.85		$825.0631	$825.06	$825.10	$825.00