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	$54.96	12.535%	$61.8492	$61.85	$61.85	$61.80
Purchase #2	$160.69	7.369%	$172.5312	$172.53	$172.55	$172.50
Purchase #3	$147.85	9.810%	$162.3541	$162.35	$162.35	$162.40
Purchase #4	$133.98	13.760%	$152.4156	$152.42	$152.40	$152.40
Purchase #5	$52.84	5.277%	$55.6284	$55.63	$55.65	$55.60
Purchase #6	$79.81	3.467%	$82.577	$82.58	$82.60	$82.60
Purchase #7	$93.51	6.615%	$99.6957	$99.70	$99.70	$99.70
7 purchase totals =	$723.64		$787.0512	$787.06	$787.10	$787.00