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	$225.84	10.248%	$248.9841	$248.98	$249.00	$249.00
Purchase #2	$107.28	3.743%	$111.2955	$111.30	$111.30	$111.30
Purchase #3	$14.57	12.383%	$16.3742	$16.37	$16.35	$16.40
Purchase #4	$226.95	8.186%	$245.5281	$245.53	$245.55	$245.50
Purchase #5	$135.60	5.172%	$142.6132	$142.61	$142.60	$142.60
Purchase #6	$154.74	11.625%	$172.7285	$172.73	$172.75	$172.70
Purchase #7	$78.29	4.587%	$81.8812	$81.88	$81.90	$81.90
7 purchase totals =	$943.27		$1,019.4048	$1,019.40	$1,019.45	$1,019.40