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	$167.78	4.857%	$175.9291	$175.93	$175.95	$175.90
Purchase #2	$203.29	6.193%	$215.8797	$215.88	$215.90	$215.90
Purchase #3	$48.96	12.138%	$54.9028	$54.90	$54.90	$54.90
Purchase #4	$227.43	9.197%	$248.3467	$248.35	$248.35	$248.30
Purchase #5	$37.40	7.840%	$40.3322	$40.33	$40.35	$40.30
Purchase #6	$63.86	5.133%	$67.1379	$67.14	$67.15	$67.10
Purchase #7	$168.71	12.559%	$189.8983	$189.90	$189.90	$189.90
7 purchase totals =	$917.43		$992.4267	$992.43	$992.50	$992.30