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	$212.50	12.404%	$238.8585	$238.86	$238.85	$238.90
Purchase #2	$48.34	13.759%	$54.9911	$54.99	$55.00	$55.00
Purchase #3	$71.52	6.270%	$76.0043	$76.00	$76.00	$76.00
Purchase #4	$249.62	10.346%	$275.4457	$275.45	$275.45	$275.40
Purchase #5	$131.60	6.671%	$140.379	$140.38	$140.40	$140.40
Purchase #6	$63.55	4.329%	$66.3011	$66.30	$66.30	$66.30
Purchase #7	$235.47	6.541%	$250.8721	$250.87	$250.85	$250.90
7 purchase totals =	$1,012.60		$1,102.8518	$1,102.85	$1,102.85	$1,102.90