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	$190.65	12.135%	$213.7854	$213.79	$213.80	$213.80
Purchase #2	$61.56	5.639%	$65.0314	$65.03	$65.05	$65.00
Purchase #3	$73.41	5.280%	$77.286	$77.29	$77.30	$77.30
Purchase #4	$192.91	6.698%	$205.8311	$205.83	$205.85	$205.80
Purchase #5	$242.94	6.206%	$258.0169	$258.02	$258.00	$258.00
Purchase #6	$78.91	4.696%	$82.6156	$82.62	$82.60	$82.60
Purchase #7	$90.85	11.230%	$101.0525	$101.05	$101.05	$101.10
7 purchase totals =	$931.23		$1,003.6189	$1,003.63	$1,003.65	$1,003.60