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	$116.87	11.559%	$130.379	$130.38	$130.40	$130.40
Purchase #2	$7.59	12.496%	$8.5384	$8.54	$8.55	$8.50
Purchase #3	$100.99	4.469%	$105.5032	$105.50	$105.50	$105.50
Purchase #4	$218.51	6.160%	$231.9702	$231.97	$231.95	$232.00
Purchase #5	$133.84	7.229%	$143.5153	$143.52	$143.50	$143.50
Purchase #6	$176.36	5.683%	$186.3825	$186.38	$186.40	$186.40
Purchase #7	$81.43	10.501%	$89.981	$89.98	$90.00	$90.00
7 purchase totals =	$835.59		$896.2696	$896.27	$896.30	$896.30