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	$142.50	5.660%	$150.5655	$150.57	$150.55	$150.60
Purchase #2	$95.32	9.231%	$104.119	$104.12	$104.10	$104.10
Purchase #3	$232.34	4.194%	$242.0843	$242.08	$242.10	$242.10
Purchase #4	$101.89	12.746%	$114.8769	$114.88	$114.90	$114.90
Purchase #5	$242.90	11.238%	$270.1971	$270.20	$270.20	$270.20
Purchase #6	$148.71	13.159%	$168.2787	$168.28	$168.30	$168.30
Purchase #7	$241.77	5.744%	$255.6573	$255.66	$255.65	$255.70
7 purchase totals =	$1,205.43		$1,305.7788	$1,305.79	$1,305.80	$1,305.90