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	$50.38	11.568%	$56.208	$56.21	$56.20	$56.20
Purchase #2	$34.50	11.496%	$38.4661	$38.47	$38.45	$38.50
Purchase #3	$76.61	11.336%	$85.2945	$85.29	$85.30	$85.30
Purchase #4	$212.59	4.685%	$222.5498	$222.55	$222.55	$222.50
Purchase #5	$230.34	4.257%	$240.1456	$240.15	$240.15	$240.10
Purchase #6	$8.88	6.464%	$9.454	$9.45	$9.45	$9.50
Purchase #7	$73.70	6.479%	$78.475	$78.48	$78.50	$78.50
7 purchase totals =	$687.00		$730.5930	$730.60	$730.60	$730.60