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	$50.93	10.646%	$56.352	$56.35	$56.35	$56.40
Purchase #2	$154.76	12.440%	$174.0121	$174.01	$174.00	$174.00
Purchase #3	$195.36	12.818%	$220.4012	$220.40	$220.40	$220.40
Purchase #4	$153.92	11.660%	$171.8671	$171.87	$171.85	$171.90
Purchase #5	$129.72	5.822%	$137.2723	$137.27	$137.25	$137.30
Purchase #6	$107.27	3.801%	$111.3473	$111.35	$111.35	$111.30
Purchase #7	$61.57	10.329%	$67.9296	$67.93	$67.95	$67.90
7 purchase totals =	$853.53		$939.1816	$939.18	$939.15	$939.20