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	$62.39	3.127%	$64.3409	$64.34	$64.35	$64.30
Purchase #2	$202.57	3.118%	$208.8861	$208.89	$208.90	$208.90
Purchase #3	$71.91	11.650%	$80.2875	$80.29	$80.30	$80.30
Purchase #4	$240.38	11.443%	$267.8867	$267.89	$267.90	$267.90
Purchase #5	$104.91	3.333%	$108.4067	$108.41	$108.40	$108.40
Purchase #6	$31.54	3.467%	$32.6335	$32.63	$32.65	$32.60
Purchase #7	$222.29	5.521%	$234.5626	$234.56	$234.55	$234.60
7 purchase totals =	$935.99		$997.0040	$997.01	$997.05	$997.00