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	$121.98	7.487%	$131.1126	$131.11	$131.10	$131.10
Purchase #2	$158.45	13.135%	$179.2624	$179.26	$179.25	$179.30
Purchase #3	$113.61	3.803%	$117.9306	$117.93	$117.95	$117.90
Purchase #4	$196.76	6.800%	$210.1397	$210.14	$210.15	$210.10
Purchase #5	$196.58	5.440%	$207.274	$207.27	$207.25	$207.30
Purchase #6	$148.61	3.334%	$153.5647	$153.56	$153.55	$153.60
Purchase #7	$134.67	8.108%	$145.589	$145.59	$145.60	$145.60
7 purchase totals =	$1,070.66		$1,144.8730	$1,144.86	$1,144.85	$1,144.90