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	$218.46	5.499%	$230.4731	$230.47	$230.45	$230.50
Purchase #2	$10.86	9.575%	$11.8998	$11.90	$11.90	$11.90
Purchase #3	$172.74	5.834%	$182.8177	$182.82	$182.80	$182.80
Purchase #4	$249.64	10.120%	$274.9036	$274.90	$274.90	$274.90
Purchase #5	$114.89	7.786%	$123.8353	$123.84	$123.85	$123.80
Purchase #6	$223.66	7.666%	$240.8058	$240.81	$240.80	$240.80
Purchase #7	$7.87	9.350%	$8.6058	$8.61	$8.60	$8.60
7 purchase totals =	$998.12		$1,073.3411	$1,073.35	$1,073.30	$1,073.30