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	$186.67	11.690%	$208.4917	$208.49	$208.50	$208.50
Purchase #2	$29.85	6.664%	$31.8392	$31.84	$31.85	$31.80
Purchase #3	$156.47	12.351%	$175.7956	$175.80	$175.80	$175.80
Purchase #4	$150.95	8.699%	$164.0811	$164.08	$164.10	$164.10
Purchase #5	$59.94	11.559%	$66.8685	$66.87	$66.85	$66.90
Purchase #6	$174.33	12.765%	$196.5832	$196.58	$196.60	$196.60
Purchase #7	$66.90	5.543%	$70.6083	$70.61	$70.60	$70.60
7 purchase totals =	$825.11		$914.2676	$914.27	$914.30	$914.30