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	$194.58	6.727%	$207.6694	$207.67	$207.65	$207.70
Purchase #2	$137.56	3.645%	$142.5741	$142.57	$142.55	$142.60
Purchase #3	$49.53	5.376%	$52.1927	$52.19	$52.20	$52.20
Purchase #4	$166.96	3.249%	$172.3845	$172.38	$172.40	$172.40
Purchase #5	$248.52	6.769%	$265.3423	$265.34	$265.35	$265.30
Purchase #6	$98.64	13.361%	$111.8193	$111.82	$111.80	$111.80
Purchase #7	$242.35	12.825%	$273.4314	$273.43	$273.45	$273.40
7 purchase totals =	$1,138.14		$1,225.4137	$1,225.40	$1,225.40	$1,225.40