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	$54.51	8.802%	$59.308	$59.31	$59.30	$59.30
Purchase #2	$84.60	5.572%	$89.3139	$89.31	$89.30	$89.30
Purchase #3	$221.79	3.235%	$228.9649	$228.96	$228.95	$229.00
Purchase #4	$152.56	5.691%	$161.2422	$161.24	$161.25	$161.20
Purchase #5	$246.45	7.684%	$265.3872	$265.39	$265.40	$265.40
Purchase #6	$7.65	8.178%	$8.2756	$8.28	$8.30	$8.30
Purchase #7	$89.53	6.178%	$95.0612	$95.06	$95.05	$95.10
7 purchase totals =	$857.09		$907.5530	$907.55	$907.55	$907.60