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	$243.33	4.303%	$253.8005	$253.80	$253.80	$253.80
Purchase #2	$176.75	5.326%	$186.1637	$186.16	$186.15	$186.20
Purchase #3	$36.49	13.780%	$41.5183	$41.52	$41.50	$41.50
Purchase #4	$233.95	10.659%	$258.8867	$258.89	$258.90	$258.90
Purchase #5	$154.37	5.560%	$162.953	$162.95	$162.95	$163.00
Purchase #6	$160.54	3.264%	$165.78	$165.78	$165.80	$165.80
Purchase #7	$190.59	13.178%	$215.706	$215.71	$215.70	$215.70
7 purchase totals =	$1,196.02		$1,284.8082	$1,284.81	$1,284.80	$1,284.90