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	$39.57	13.307%	$44.8356	$44.84	$44.85	$44.80
Purchase #2	$82.82	9.292%	$90.5156	$90.52	$90.50	$90.50
Purchase #3	$157.86	9.109%	$172.2395	$172.24	$172.25	$172.20
Purchase #4	$192.70	10.360%	$212.6637	$212.66	$212.65	$212.70
Purchase #5	$215.61	10.631%	$238.5315	$238.53	$238.55	$238.50
Purchase #6	$250.59	7.151%	$268.5097	$268.51	$268.50	$268.50
Purchase #7	$48.73	7.198%	$52.2376	$52.24	$52.25	$52.20
7 purchase totals =	$987.88		$1,079.5332	$1,079.54	$1,079.55	$1,079.40