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	$131.60	9.189%	$143.6927	$143.69	$143.70	$143.70
Purchase #2	$168.50	11.557%	$187.9735	$187.97	$187.95	$188.00
Purchase #3	$174.88	8.805%	$190.2782	$190.28	$190.30	$190.30
Purchase #4	$99.36	9.824%	$109.1211	$109.12	$109.10	$109.10
Purchase #5	$155.37	10.646%	$171.9107	$171.91	$171.90	$171.90
Purchase #6	$111.86	5.424%	$117.9273	$117.93	$117.95	$117.90
Purchase #7	$144.31	5.367%	$152.0551	$152.06	$152.05	$152.10
7 purchase totals =	$985.88		$1,072.9586	$1,072.96	$1,072.95	$1,073.00