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	$212.46	3.803%	$220.5399	$220.54	$220.55	$220.50
Purchase #2	$116.61	10.749%	$129.1444	$129.14	$129.15	$129.10
Purchase #3	$86.59	3.147%	$89.315	$89.32	$89.30	$89.30
Purchase #4	$103.83	5.611%	$109.6559	$109.66	$109.65	$109.70
Purchase #5	$209.70	3.222%	$216.4565	$216.46	$216.45	$216.50
Purchase #6	$242.76	13.167%	$274.7242	$274.72	$274.70	$274.70
Purchase #7	$126.42	9.292%	$138.1669	$138.17	$138.15	$138.20
7 purchase totals =	$1,098.37		$1,178.0028	$1,178.01	$1,177.95	$1,178.00