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	$186.34	4.336%	$194.4197	$194.42	$194.40	$194.40
Purchase #2	$230.94	3.292%	$238.5425	$238.54	$238.55	$238.50
Purchase #3	$231.51	13.586%	$262.9629	$262.96	$262.95	$263.00
Purchase #4	$57.58	5.541%	$60.7705	$60.77	$60.75	$60.80
Purchase #5	$117.77	4.711%	$123.3181	$123.32	$123.30	$123.30
Purchase #6	$103.66	12.347%	$116.4589	$116.46	$116.45	$116.50
Purchase #7	$131.57	6.671%	$140.347	$140.35	$140.35	$140.30
7 purchase totals =	$1,059.37		$1,136.8196	$1,136.82	$1,136.75	$1,136.80