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	$146.94	12.253%	$164.9446	$164.94	$164.95	$164.90
Purchase #2	$136.60	11.729%	$152.6218	$152.62	$152.60	$152.60
Purchase #3	$190.91	9.804%	$209.6268	$209.63	$209.65	$209.60
Purchase #4	$92.83	7.189%	$99.5035	$99.50	$99.50	$99.50
Purchase #5	$97.70	12.376%	$109.7914	$109.79	$109.80	$109.80
Purchase #6	$164.54	6.143%	$174.6477	$174.65	$174.65	$174.60
Purchase #7	$190.29	6.731%	$203.0984	$203.10	$203.10	$203.10
7 purchase totals =	$1,019.81		$1,114.2342	$1,114.23	$1,114.25	$1,114.10