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	$240.68	11.768%	$269.0032	$269.00	$269.00	$269.00
Purchase #2	$105.36	5.393%	$111.0421	$111.04	$111.05	$111.00
Purchase #3	$234.64	4.133%	$244.3377	$244.34	$244.35	$244.30
Purchase #4	$93.51	12.604%	$105.296	$105.30	$105.30	$105.30
Purchase #5	$164.35	13.595%	$186.6934	$186.69	$186.70	$186.70
Purchase #6	$210.35	10.249%	$231.9088	$231.91	$231.90	$231.90
Purchase #7	$143.41	6.652%	$152.9496	$152.95	$152.95	$152.90
7 purchase totals =	$1,192.30		$1,301.2308	$1,301.23	$1,301.25	$1,301.10