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	$181.77	7.850%	$196.0389	$196.04	$196.05	$196.00
Purchase #2	$233.77	8.600%	$253.8742	$253.87	$253.85	$253.90
Purchase #3	$61.39	3.165%	$63.333	$63.33	$63.35	$63.30
Purchase #4	$95.66	3.746%	$99.2434	$99.24	$99.25	$99.20
Purchase #5	$195.42	6.743%	$208.5972	$208.60	$208.60	$208.60
Purchase #6	$31.60	7.666%	$34.0225	$34.02	$34.00	$34.00
Purchase #7	$107.87	3.645%	$111.8019	$111.80	$111.80	$111.80
7 purchase totals =	$907.48		$966.9111	$966.90	$966.90	$966.80