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	$163.41	6.790%	$174.5055	$174.51	$174.50	$174.50
Purchase #2	$62.94	11.555%	$70.2127	$70.21	$70.20	$70.20
Purchase #3	$105.72	5.451%	$111.4828	$111.48	$111.50	$111.50
Purchase #4	$141.91	10.257%	$156.4657	$156.47	$156.45	$156.50
Purchase #5	$155.29	8.383%	$168.308	$168.31	$168.30	$168.30
Purchase #6	$104.30	3.724%	$108.1841	$108.18	$108.20	$108.20
Purchase #7	$235.27	3.354%	$243.161	$243.16	$243.15	$243.20
7 purchase totals =	$968.84		$1,032.3198	$1,032.32	$1,032.30	$1,032.40