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	$62.86	13.399%	$71.2826	$71.28	$71.30	$71.30
Purchase #2	$150.54	9.490%	$164.8262	$164.83	$164.85	$164.80
Purchase #3	$38.77	5.854%	$41.0396	$41.04	$41.05	$41.00
Purchase #4	$211.39	8.560%	$229.485	$229.49	$229.50	$229.50
Purchase #5	$224.37	10.262%	$247.3948	$247.39	$247.40	$247.40
Purchase #6	$92.32	4.453%	$96.431	$96.43	$96.45	$96.40
Purchase #7	$97.39	7.713%	$104.9017	$104.90	$104.90	$104.90
7 purchase totals =	$877.64		$955.3609	$955.36	$955.45	$955.30