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	$172.28	7.731%	$185.599	$185.60	$185.60	$185.60
Purchase #2	$19.50	5.756%	$20.6224	$20.62	$20.60	$20.60
Purchase #3	$105.87	6.599%	$112.8564	$112.86	$112.85	$112.90
Purchase #4	$163.48	4.495%	$170.8284	$170.83	$170.85	$170.80
Purchase #5	$178.49	11.140%	$198.3738	$198.37	$198.35	$198.40
Purchase #6	$115.92	9.468%	$126.8953	$126.90	$126.90	$126.90
Purchase #7	$237.26	9.464%	$259.7143	$259.71	$259.70	$259.70
7 purchase totals =	$992.80		$1,074.8896	$1,074.89	$1,074.85	$1,074.90