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	$186.77	3.147%	$192.6477	$192.65	$192.65	$192.60
Purchase #2	$90.30	10.276%	$99.5792	$99.58	$99.60	$99.60
Purchase #3	$244.51	13.135%	$276.6264	$276.63	$276.65	$276.60
Purchase #4	$205.69	3.800%	$213.5062	$213.51	$213.50	$213.50
Purchase #5	$172.72	9.194%	$188.5999	$188.60	$188.60	$188.60
Purchase #6	$127.40	11.164%	$141.6229	$141.62	$141.60	$141.60
Purchase #7	$247.59	9.779%	$271.8018	$271.80	$271.80	$271.80
7 purchase totals =	$1,274.98		$1,384.3841	$1,384.39	$1,384.40	$1,384.30