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	$63.72	10.800%	$70.6018	$70.60	$70.60	$70.60
Purchase #2	$177.55	5.825%	$187.8923	$187.89	$187.90	$187.90
Purchase #3	$131.87	6.833%	$140.8807	$140.88	$140.90	$140.90
Purchase #4	$104.39	6.857%	$111.548	$111.55	$111.55	$111.50
Purchase #5	$26.32	7.727%	$28.3537	$28.35	$28.35	$28.40
Purchase #6	$216.60	7.477%	$232.7952	$232.80	$232.80	$232.80
Purchase #7	$229.27	5.221%	$241.2402	$241.24	$241.25	$241.20
7 purchase totals =	$949.72		$1,013.3119	$1,013.31	$1,013.35	$1,013.30