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	$249.42	5.702%	$263.6419	$263.64	$263.65	$263.60
Purchase #2	$138.38	11.514%	$154.3131	$154.31	$154.30	$154.30
Purchase #3	$35.85	10.185%	$39.5013	$39.50	$39.50	$39.50
Purchase #4	$116.32	9.471%	$127.3367	$127.34	$127.35	$127.30
Purchase #5	$218.50	7.854%	$235.661	$235.66	$235.65	$235.70
Purchase #6	$61.79	8.374%	$66.9643	$66.96	$66.95	$67.00
Purchase #7	$178.35	5.441%	$188.054	$188.05	$188.05	$188.10
7 purchase totals =	$998.61		$1,075.4723	$1,075.46	$1,075.45	$1,075.50