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	$6.25	12.214%	$7.0134	$7.01	$7.00	$7.00
Purchase #2	$40.81	11.278%	$45.4126	$45.41	$45.40	$45.40
Purchase #3	$79.28	12.628%	$89.2915	$89.29	$89.30	$89.30
Purchase #4	$63.34	8.832%	$68.9342	$68.93	$68.95	$68.90
Purchase #5	$124.80	3.272%	$128.8835	$128.88	$128.90	$128.90
Purchase #6	$111.54	13.476%	$126.5711	$126.57	$126.55	$126.60
Purchase #7	$64.33	4.820%	$67.4307	$67.43	$67.45	$67.40
7 purchase totals =	$490.35		$533.5370	$533.52	$533.55	$533.50