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	$197.95	13.802%	$225.2711	$225.27	$225.25	$225.30
Purchase #2	$218.51	12.190%	$245.1464	$245.15	$245.15	$245.10
Purchase #3	$42.72	4.106%	$44.4741	$44.47	$44.45	$44.50
Purchase #4	$97.45	6.274%	$103.564	$103.56	$103.55	$103.60
Purchase #5	$132.73	4.256%	$138.379	$138.38	$138.40	$138.40
Purchase #6	$59.46	13.620%	$67.5585	$67.56	$67.55	$67.60
Purchase #7	$104.81	13.351%	$118.8032	$118.80	$118.80	$118.80
7 purchase totals =	$853.63		$943.1963	$943.19	$943.15	$943.30