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	$109.87	3.440%	$113.6495	$113.65	$113.65	$113.60
Purchase #2	$163.42	5.239%	$171.9816	$171.98	$172.00	$172.00
Purchase #3	$173.89	10.610%	$192.3397	$192.34	$192.35	$192.30
Purchase #4	$121.74	12.687%	$137.1852	$137.19	$137.20	$137.20
Purchase #5	$171.25	10.227%	$188.7637	$188.76	$188.75	$188.80
Purchase #6	$163.69	5.380%	$172.4965	$172.50	$172.50	$172.50
Purchase #7	$104.98	4.230%	$109.4207	$109.42	$109.40	$109.40
7 purchase totals =	$1,008.84		$1,085.8369	$1,085.84	$1,085.85	$1,085.80