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	$134.37	4.666%	$140.6397	$140.64	$140.65	$140.60
Purchase #2	$248.95	6.559%	$265.2786	$265.28	$265.30	$265.30
Purchase #3	$34.87	8.301%	$37.7646	$37.76	$37.75	$37.80
Purchase #4	$95.85	6.784%	$102.3525	$102.35	$102.35	$102.40
Purchase #5	$186.32	3.340%	$192.5431	$192.54	$192.55	$192.50
Purchase #6	$48.86	9.448%	$53.4763	$53.48	$53.50	$53.50
Purchase #7	$56.45	5.273%	$59.4266	$59.43	$59.45	$59.40
7 purchase totals =	$805.67		$851.4814	$851.48	$851.55	$851.50