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	$157.29	5.175%	$165.4298	$165.43	$165.45	$165.40
Purchase #2	$78.96	3.235%	$81.5144	$81.51	$81.50	$81.50
Purchase #3	$179.96	9.223%	$196.5577	$196.56	$196.55	$196.60
Purchase #4	$116.76	9.626%	$127.9993	$128.00	$128.00	$128.00
Purchase #5	$5.77	12.634%	$6.499	$6.50	$6.50	$6.50
Purchase #6	$174.62	12.351%	$196.1873	$196.19	$196.20	$196.20
Purchase #7	$238.27	5.754%	$251.9801	$251.98	$252.00	$252.00
7 purchase totals =	$951.63		$1,026.1676	$1,026.17	$1,026.20	$1,026.20