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	$248.89	8.845%	$270.9043	$270.90	$270.90	$270.90
Purchase #2	$18.58	12.740%	$20.9471	$20.95	$20.95	$20.90
Purchase #3	$215.71	11.429%	$240.3635	$240.36	$240.35	$240.40
Purchase #4	$139.68	4.192%	$145.5354	$145.54	$145.55	$145.50
Purchase #5	$102.50	6.870%	$109.5418	$109.54	$109.55	$109.50
Purchase #6	$153.47	9.157%	$167.5232	$167.52	$167.50	$167.50
Purchase #7	$86.92	8.785%	$94.5559	$94.56	$94.55	$94.60
7 purchase totals =	$965.75		$1,049.3712	$1,049.37	$1,049.35	$1,049.30