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	$211.65	5.146%	$222.5415	$222.54	$222.55	$222.50
Purchase #2	$29.46	12.674%	$33.1938	$33.19	$33.20	$33.20
Purchase #3	$184.28	6.447%	$196.1605	$196.16	$196.15	$196.20
Purchase #4	$103.42	6.319%	$109.9551	$109.96	$109.95	$110.00
Purchase #5	$26.54	5.382%	$27.9684	$27.97	$27.95	$28.00
Purchase #6	$222.31	9.232%	$242.8337	$242.83	$242.85	$242.80
Purchase #7	$43.57	9.212%	$47.5837	$47.58	$47.60	$47.60
7 purchase totals =	$821.23		$880.2367	$880.23	$880.25	$880.30