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	$178.90	9.591%	$196.0583	$196.06	$196.05	$196.10
Purchase #2	$99.94	5.104%	$105.0409	$105.04	$105.05	$105.00
Purchase #3	$31.84	13.573%	$36.1616	$36.16	$36.15	$36.20
Purchase #4	$205.62	13.796%	$233.9873	$233.99	$234.00	$234.00
Purchase #5	$59.77	10.552%	$66.0769	$66.08	$66.10	$66.10
Purchase #6	$45.41	13.240%	$51.4223	$51.42	$51.40	$51.40
Purchase #7	$119.37	3.253%	$123.2531	$123.25	$123.25	$123.30
7 purchase totals =	$740.85		$812.0004	$812.00	$812.00	$812.10