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	$37.98	10.278%	$41.8836	$41.88	$41.90	$41.90
Purchase #2	$214.34	6.599%	$228.4843	$228.48	$228.50	$228.50
Purchase #3	$111.64	4.627%	$116.8056	$116.81	$116.80	$116.80
Purchase #4	$174.93	10.215%	$192.7991	$192.80	$192.80	$192.80
Purchase #5	$179.95	5.755%	$190.3061	$190.31	$190.30	$190.30
Purchase #6	$71.90	13.486%	$81.5964	$81.60	$81.60	$81.60
Purchase #7	$171.66	4.402%	$179.2165	$179.22	$179.20	$179.20
7 purchase totals =	$962.40		$1,031.0916	$1,031.10	$1,031.10	$1,031.10