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	$200.80	7.739%	$216.3399	$216.34	$216.35	$216.30
Purchase #2	$229.36	13.186%	$259.6034	$259.60	$259.60	$259.60
Purchase #3	$17.35	6.563%	$18.4887	$18.49	$18.50	$18.50
Purchase #4	$215.66	3.569%	$223.3569	$223.36	$223.35	$223.40
Purchase #5	$101.29	7.780%	$109.1704	$109.17	$109.15	$109.20
Purchase #6	$38.83	9.602%	$42.5585	$42.56	$42.55	$42.60
Purchase #7	$57.57	8.410%	$62.4116	$62.41	$62.40	$62.40
7 purchase totals =	$860.86		$931.9294	$931.93	$931.90	$932.00