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	$15.72	7.197%	$16.8514	$16.85	$16.85	$16.90
Purchase #2	$242.65	7.336%	$260.4508	$260.45	$260.45	$260.50
Purchase #3	$49.90	6.304%	$53.0457	$53.05	$53.05	$53.00
Purchase #4	$205.54	13.546%	$233.3824	$233.38	$233.40	$233.40
Purchase #5	$186.39	12.341%	$209.3924	$209.39	$209.40	$209.40
Purchase #6	$87.59	12.373%	$98.4275	$98.43	$98.45	$98.40
Purchase #7	$126.66	3.597%	$131.216	$131.22	$131.20	$131.20
7 purchase totals =	$914.45		$1,002.7662	$1,002.77	$1,002.80	$1,002.80