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	$209.81	11.500%	$233.9382	$233.94	$233.95	$233.90
Purchase #2	$116.38	13.290%	$131.8469	$131.85	$131.85	$131.80
Purchase #3	$78.36	9.509%	$85.8113	$85.81	$85.80	$85.80
Purchase #4	$50.29	11.684%	$56.1659	$56.17	$56.15	$56.20
Purchase #5	$47.54	4.667%	$49.7587	$49.76	$49.75	$49.80
Purchase #6	$73.69	9.711%	$80.846	$80.85	$80.85	$80.80
Purchase #7	$148.46	10.687%	$164.3259	$164.33	$164.35	$164.30
7 purchase totals =	$724.53		$802.6929	$802.71	$802.70	$802.60