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	$132.92	7.152%	$142.4264	$142.43	$142.45	$142.40
Purchase #2	$13.98	9.741%	$15.3418	$15.34	$15.35	$15.30
Purchase #3	$209.29	6.492%	$222.8771	$222.88	$222.90	$222.90
Purchase #4	$10.56	3.111%	$10.8885	$10.89	$10.90	$10.90
Purchase #5	$179.56	6.119%	$190.5473	$190.55	$190.55	$190.50
Purchase #6	$233.58	4.300%	$243.6239	$243.62	$243.60	$243.60
Purchase #7	$39.59	3.566%	$41.0018	$41.00	$41.00	$41.00
7 purchase totals =	$819.48		$866.7068	$866.71	$866.75	$866.60