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	$92.55	12.797%	$104.3936	$104.39	$104.40	$104.40
Purchase #2	$191.94	8.371%	$208.0073	$208.01	$208.00	$208.00
Purchase #3	$26.83	11.512%	$29.9187	$29.92	$29.90	$29.90
Purchase #4	$145.90	8.555%	$158.3817	$158.38	$158.40	$158.40
Purchase #5	$235.72	4.276%	$245.7994	$245.80	$245.80	$245.80
Purchase #6	$83.75	10.397%	$92.4575	$92.46	$92.45	$92.50
Purchase #7	$148.31	13.250%	$167.9611	$167.96	$167.95	$168.00
7 purchase totals =	$925.00		$1,006.9193	$1,006.92	$1,006.90	$1,007.00