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	$124.96	8.440%	$135.5066	$135.51	$135.50	$135.50
Purchase #2	$129.76	9.679%	$142.3195	$142.32	$142.30	$142.30
Purchase #3	$123.49	13.386%	$140.0204	$140.02	$140.00	$140.00
Purchase #4	$247.76	11.241%	$275.6107	$275.61	$275.60	$275.60
Purchase #5	$44.84	3.710%	$46.5036	$46.50	$46.50	$46.50
Purchase #6	$233.58	6.121%	$247.8774	$247.88	$247.90	$247.90
Purchase #7	$141.34	10.724%	$156.4973	$156.50	$156.50	$156.50
7 purchase totals =	$1,045.73		$1,144.3355	$1,144.34	$1,144.30	$1,144.30