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	$55.44	12.798%	$62.5352	$62.54	$62.55	$62.50
Purchase #2	$111.29	11.639%	$124.243	$124.24	$124.25	$124.20
Purchase #3	$210.39	10.830%	$233.1752	$233.18	$233.20	$233.20
Purchase #4	$200.84	11.720%	$224.3784	$224.38	$224.40	$224.40
Purchase #5	$74.65	3.483%	$77.2501	$77.25	$77.25	$77.30
Purchase #6	$244.77	5.863%	$259.1209	$259.12	$259.10	$259.10
Purchase #7	$117.78	11.376%	$131.1787	$131.18	$131.20	$131.20
7 purchase totals =	$1,015.16		$1,111.8815	$1,111.89	$1,111.95	$1,111.90