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	$144.65	9.160%	$157.8999	$157.90	$157.90	$157.90
Purchase #2	$126.90	3.843%	$131.7768	$131.78	$131.80	$131.80
Purchase #3	$33.83	7.239%	$36.279	$36.28	$36.30	$36.30
Purchase #4	$12.83	4.250%	$13.3753	$13.38	$13.40	$13.40
Purchase #5	$192.38	4.456%	$200.9525	$200.95	$200.95	$201.00
Purchase #6	$231.83	10.820%	$256.914	$256.91	$256.90	$256.90
Purchase #7	$24.28	11.638%	$27.1057	$27.11	$27.10	$27.10
7 purchase totals =	$766.70		$824.3032	$824.31	$824.35	$824.40