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	$204.40	10.539%	$225.9417	$225.94	$225.95	$225.90
Purchase #2	$198.43	12.290%	$222.817	$222.82	$222.80	$222.80
Purchase #3	$71.97	3.221%	$74.2882	$74.29	$74.30	$74.30
Purchase #4	$72.81	4.111%	$75.8032	$75.80	$75.80	$75.80
Purchase #5	$214.52	4.374%	$223.9031	$223.90	$223.90	$223.90
Purchase #6	$67.94	6.551%	$72.3907	$72.39	$72.40	$72.40
Purchase #7	$207.93	9.398%	$227.4713	$227.47	$227.45	$227.50
7 purchase totals =	$1,038.00		$1,122.6152	$1,122.61	$1,122.60	$1,122.60