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	$148.93	5.133%	$156.5746	$156.57	$156.55	$156.60
Purchase #2	$206.34	10.131%	$227.2443	$227.24	$227.25	$227.20
Purchase #3	$38.43	7.349%	$41.2542	$41.25	$41.25	$41.30
Purchase #4	$237.92	11.194%	$264.5528	$264.55	$264.55	$264.60
Purchase #5	$81.58	9.561%	$89.3799	$89.38	$89.40	$89.40
Purchase #6	$204.84	13.149%	$231.7744	$231.77	$231.75	$231.80
Purchase #7	$250.36	10.854%	$277.5341	$277.53	$277.55	$277.50
7 purchase totals =	$1,168.40		$1,288.3143	$1,288.29	$1,288.30	$1,288.40