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	$201.75	7.773%	$217.432	$217.43	$217.45	$217.40
Purchase #2	$99.85	11.646%	$111.4785	$111.48	$111.50	$111.50
Purchase #3	$80.79	4.441%	$84.3779	$84.38	$84.40	$84.40
Purchase #4	$233.64	11.165%	$259.7259	$259.73	$259.75	$259.70
Purchase #5	$75.54	6.517%	$80.4629	$80.46	$80.45	$80.50
Purchase #6	$179.35	5.540%	$189.286	$189.29	$189.30	$189.30
Purchase #7	$105.32	3.373%	$108.8724	$108.87	$108.85	$108.90
7 purchase totals =	$976.24		$1,051.6356	$1,051.64	$1,051.70	$1,051.70