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	$218.25	10.271%	$240.6665	$240.67	$240.65	$240.70
Purchase #2	$128.31	8.735%	$139.5179	$139.52	$139.50	$139.50
Purchase #3	$249.84	4.601%	$261.3351	$261.34	$261.35	$261.30
Purchase #4	$110.80	3.509%	$114.688	$114.69	$114.70	$114.70
Purchase #5	$172.91	8.586%	$187.7561	$187.76	$187.75	$187.80
Purchase #6	$105.50	3.503%	$109.1957	$109.20	$109.20	$109.20
Purchase #7	$106.75	4.421%	$111.4694	$111.47	$111.45	$111.50
7 purchase totals =	$1,092.36		$1,164.6287	$1,164.65	$1,164.60	$1,164.70