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	$213.79	11.363%	$238.083	$238.08	$238.10	$238.10
Purchase #2	$23.62	9.333%	$25.8245	$25.82	$25.80	$25.80
Purchase #3	$65.68	10.767%	$72.7518	$72.75	$72.75	$72.80
Purchase #4	$103.57	11.206%	$115.1761	$115.18	$115.20	$115.20
Purchase #5	$39.71	13.626%	$45.1209	$45.12	$45.10	$45.10
Purchase #6	$39.42	7.203%	$42.2594	$42.26	$42.25	$42.30
Purchase #7	$141.84	3.151%	$146.3094	$146.31	$146.30	$146.30
7 purchase totals =	$627.63		$685.5251	$685.52	$685.50	$685.60