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	$137.43	9.649%	$150.6906	$150.69	$150.70	$150.70
Purchase #2	$144.25	5.808%	$152.628	$152.63	$152.65	$152.60
Purchase #3	$64.69	10.336%	$71.3764	$71.38	$71.40	$71.40
Purchase #4	$120.40	3.638%	$124.7802	$124.78	$124.80	$124.80
Purchase #5	$7.83	3.699%	$8.1196	$8.12	$8.10	$8.10
Purchase #6	$12.59	7.609%	$13.548	$13.55	$13.55	$13.50
Purchase #7	$177.32	10.715%	$196.3198	$196.32	$196.30	$196.30
7 purchase totals =	$664.51		$717.4626	$717.47	$717.50	$717.40