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	$222.30	5.757%	$235.0978	$235.10	$235.10	$235.10
Purchase #2	$245.32	10.619%	$271.3705	$271.37	$271.35	$271.40
Purchase #3	$59.31	6.473%	$63.1491	$63.15	$63.15	$63.10
Purchase #4	$215.36	12.442%	$242.1551	$242.16	$242.15	$242.20
Purchase #5	$60.85	9.162%	$66.4251	$66.43	$66.45	$66.40
Purchase #6	$78.97	13.356%	$89.5172	$89.52	$89.50	$89.50
Purchase #7	$45.37	4.149%	$47.2524	$47.25	$47.25	$47.30
7 purchase totals =	$927.48		$1,014.9672	$1,014.98	$1,014.95	$1,015.00