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	$98.81	12.864%	$111.5209	$111.52	$111.50	$111.50
Purchase #2	$154.53	12.830%	$174.3562	$174.36	$174.35	$174.40
Purchase #3	$101.65	3.832%	$105.5452	$105.55	$105.55	$105.50
Purchase #4	$225.77	5.379%	$237.9142	$237.91	$237.90	$237.90
Purchase #5	$115.82	10.165%	$127.5931	$127.59	$127.60	$127.60
Purchase #6	$78.87	12.147%	$88.4503	$88.45	$88.45	$88.50
Purchase #7	$186.88	8.150%	$202.1107	$202.11	$202.10	$202.10
7 purchase totals =	$962.33		$1,047.4906	$1,047.49	$1,047.45	$1,047.50