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	$173.61	13.203%	$196.5317	$196.53	$196.55	$196.50
Purchase #2	$137.39	7.602%	$147.8344	$147.83	$147.85	$147.80
Purchase #3	$152.46	6.600%	$162.5224	$162.52	$162.50	$162.50
Purchase #4	$71.63	10.844%	$79.3976	$79.40	$79.40	$79.40
Purchase #5	$82.47	6.260%	$87.6326	$87.63	$87.65	$87.60
Purchase #6	$49.84	5.866%	$52.7636	$52.76	$52.75	$52.80
Purchase #7	$15.42	3.432%	$15.9492	$15.95	$15.95	$15.90
7 purchase totals =	$682.82		$742.6315	$742.62	$742.65	$742.50