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	$76.78	7.756%	$82.7351	$82.74	$82.75	$82.70
Purchase #2	$114.83	9.127%	$125.3105	$125.31	$125.30	$125.30
Purchase #3	$222.46	5.460%	$234.6063	$234.61	$234.60	$234.60
Purchase #4	$29.43	10.166%	$32.4219	$32.42	$32.40	$32.40
Purchase #5	$54.70	6.527%	$58.2703	$58.27	$58.25	$58.30
Purchase #6	$85.58	10.351%	$94.4384	$94.44	$94.45	$94.40
Purchase #7	$162.57	10.127%	$179.0335	$179.03	$179.05	$179.00
7 purchase totals =	$746.35		$806.8160	$806.82	$806.80	$806.70