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	$67.27	5.869%	$71.2181	$71.22	$71.20	$71.20
Purchase #2	$232.95	12.544%	$262.1712	$262.17	$262.15	$262.20
Purchase #3	$52.54	5.597%	$55.4807	$55.48	$55.50	$55.50
Purchase #4	$68.88	13.287%	$78.0321	$78.03	$78.05	$78.00
Purchase #5	$76.72	12.714%	$86.4742	$86.47	$86.45	$86.50
Purchase #6	$7.37	12.539%	$8.2941	$8.29	$8.30	$8.30
Purchase #7	$157.94	6.786%	$168.6578	$168.66	$168.65	$168.70
7 purchase totals =	$663.67		$730.3282	$730.32	$730.30	$730.40