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	$117.98	11.602%	$131.668	$131.67	$131.65	$131.70
Purchase #2	$19.50	7.280%	$20.9196	$20.92	$20.90	$20.90
Purchase #3	$27.91	5.372%	$29.4093	$29.41	$29.40	$29.40
Purchase #4	$109.36	8.218%	$118.3472	$118.35	$118.35	$118.30
Purchase #5	$233.79	12.386%	$262.7472	$262.75	$262.75	$262.70
Purchase #6	$130.85	12.244%	$146.8713	$146.87	$146.85	$146.90
Purchase #7	$144.67	4.345%	$150.9559	$150.96	$150.95	$151.00
7 purchase totals =	$784.06		$860.9185	$860.93	$860.85	$860.90