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	$206.45	7.851%	$222.6584	$222.66	$222.65	$222.70
Purchase #2	$167.87	11.621%	$187.3782	$187.38	$187.40	$187.40
Purchase #3	$90.78	7.166%	$97.2853	$97.29	$97.30	$97.30
Purchase #4	$43.53	6.279%	$46.2632	$46.26	$46.25	$46.30
Purchase #5	$241.40	5.219%	$253.9987	$254.00	$254.00	$254.00
Purchase #6	$140.59	10.316%	$155.0933	$155.09	$155.10	$155.10
Purchase #7	$74.31	6.226%	$78.9365	$78.94	$78.95	$78.90
7 purchase totals =	$964.93		$1,041.6136	$1,041.62	$1,041.65	$1,041.70