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	$105.43	12.286%	$118.3831	$118.38	$118.40	$118.40
Purchase #2	$10.35	5.389%	$10.9078	$10.91	$10.90	$10.90
Purchase #3	$76.96	12.374%	$86.483	$86.48	$86.50	$86.50
Purchase #4	$91.64	12.431%	$103.0318	$103.03	$103.05	$103.00
Purchase #5	$123.87	7.276%	$132.8828	$132.88	$132.90	$132.90
Purchase #6	$201.61	7.123%	$215.9707	$215.97	$215.95	$216.00
Purchase #7	$140.30	5.869%	$148.5342	$148.53	$148.55	$148.50
7 purchase totals =	$750.16		$816.1934	$816.18	$816.25	$816.20