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	$133.42	9.551%	$146.1629	$146.16	$146.15	$146.20
Purchase #2	$154.89	12.853%	$174.798	$174.80	$174.80	$174.80
Purchase #3	$222.87	4.850%	$233.6792	$233.68	$233.70	$233.70
Purchase #4	$52.33	12.684%	$58.9675	$58.97	$58.95	$59.00
Purchase #5	$186.67	11.864%	$208.8165	$208.82	$208.80	$208.80
Purchase #6	$139.31	10.473%	$153.8999	$153.90	$153.90	$153.90
Purchase #7	$74.80	9.793%	$82.1252	$82.13	$82.15	$82.10
7 purchase totals =	$964.29		$1,058.4492	$1,058.46	$1,058.45	$1,058.50