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	$71.39	9.405%	$78.1042	$78.10	$78.10	$78.10
Purchase #2	$227.85	11.258%	$253.5014	$253.50	$253.50	$253.50
Purchase #3	$142.68	8.215%	$154.4012	$154.40	$154.40	$154.40
Purchase #4	$230.57	6.793%	$246.2326	$246.23	$246.25	$246.20
Purchase #5	$103.38	13.210%	$117.0365	$117.04	$117.05	$117.00
Purchase #6	$184.62	13.807%	$210.1105	$210.11	$210.10	$210.10
Purchase #7	$54.41	8.581%	$59.0789	$59.08	$59.10	$59.10
7 purchase totals =	$1,014.90		$1,118.4653	$1,118.46	$1,118.50	$1,118.40