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	$164.72	5.734%	$174.165	$174.17	$174.15	$174.20
Purchase #2	$221.92	7.523%	$238.615	$238.62	$238.60	$238.60
Purchase #3	$68.86	13.151%	$77.9158	$77.92	$77.90	$77.90
Purchase #4	$122.31	7.625%	$131.6361	$131.64	$131.65	$131.60
Purchase #5	$200.63	7.428%	$215.5328	$215.53	$215.55	$215.50
Purchase #6	$6.90	10.410%	$7.6183	$7.62	$7.60	$7.60
Purchase #7	$203.59	6.761%	$217.3547	$217.35	$217.35	$217.40
7 purchase totals =	$988.93		$1,062.8377	$1,062.85	$1,062.80	$1,062.80