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	$142.93	5.306%	$150.5139	$150.51	$150.50	$150.50
Purchase #2	$146.93	10.352%	$162.1402	$162.14	$162.15	$162.10
Purchase #3	$92.46	6.531%	$98.4986	$98.50	$98.50	$98.50
Purchase #4	$203.27	7.684%	$218.8893	$218.89	$218.90	$218.90
Purchase #5	$120.71	10.350%	$133.2035	$133.20	$133.20	$133.20
Purchase #6	$217.83	5.343%	$229.4687	$229.47	$229.45	$229.50
Purchase #7	$226.45	12.819%	$255.4786	$255.48	$255.50	$255.50
7 purchase totals =	$1,150.58		$1,248.1928	$1,248.19	$1,248.20	$1,248.20