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	$147.82	8.198%	$159.9383	$159.94	$159.95	$159.90
Purchase #2	$118.51	10.620%	$131.0958	$131.10	$131.10	$131.10
Purchase #3	$29.91	4.623%	$31.2927	$31.29	$31.30	$31.30
Purchase #4	$33.33	6.545%	$35.5114	$35.51	$35.50	$35.50
Purchase #5	$135.85	10.356%	$149.9186	$149.92	$149.90	$149.90
Purchase #6	$38.78	13.235%	$43.9125	$43.91	$43.90	$43.90
Purchase #7	$231.53	8.381%	$250.9345	$250.93	$250.95	$250.90
7 purchase totals =	$735.73		$802.6038	$802.60	$802.60	$802.50