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	$199.61	5.506%	$210.6005	$210.60	$210.60	$210.60
Purchase #2	$80.33	3.234%	$82.9279	$82.93	$82.95	$82.90
Purchase #3	$228.28	4.490%	$238.5298	$238.53	$238.55	$238.50
Purchase #4	$172.85	4.490%	$180.611	$180.61	$180.60	$180.60
Purchase #5	$37.98	9.470%	$41.5767	$41.58	$41.60	$41.60
Purchase #6	$176.59	12.173%	$198.0863	$198.09	$198.10	$198.10
Purchase #7	$150.53	9.130%	$164.2734	$164.27	$164.25	$164.30
7 purchase totals =	$1,046.17		$1,116.6056	$1,116.61	$1,116.65	$1,116.60