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	$217.61	12.755%	$245.3662	$245.37	$245.35	$245.40
Purchase #2	$22.49	7.559%	$24.19	$24.19	$24.20	$24.20
Purchase #3	$179.59	3.445%	$185.7769	$185.78	$185.80	$185.80
Purchase #4	$112.83	7.523%	$121.3182	$121.32	$121.30	$121.30
Purchase #5	$31.56	12.773%	$35.5912	$35.59	$35.60	$35.60
Purchase #6	$240.50	3.697%	$249.3913	$249.39	$249.40	$249.40
Purchase #7	$179.79	4.841%	$188.4936	$188.49	$188.50	$188.50
7 purchase totals =	$984.37		$1,050.1274	$1,050.13	$1,050.15	$1,050.20