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	$116.94	9.112%	$127.5956	$127.60	$127.60	$127.60
Purchase #2	$124.79	13.802%	$142.0135	$142.01	$142.00	$142.00
Purchase #3	$174.47	6.672%	$186.1106	$186.11	$186.10	$186.10
Purchase #4	$18.85	10.326%	$20.7965	$20.80	$20.80	$20.80
Purchase #5	$18.67	7.311%	$20.035	$20.04	$20.05	$20.00
Purchase #6	$126.42	10.740%	$139.9975	$140.00	$140.00	$140.00
Purchase #7	$203.39	5.556%	$214.6903	$214.69	$214.70	$214.70
7 purchase totals =	$783.53		$851.2390	$851.25	$851.25	$851.20