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	$23.56	4.208%	$24.5514	$24.55	$24.55	$24.60
Purchase #2	$29.50	6.181%	$31.3234	$31.32	$31.30	$31.30
Purchase #3	$179.25	9.583%	$196.4275	$196.43	$196.45	$196.40
Purchase #4	$41.83	13.540%	$47.4938	$47.49	$47.50	$47.50
Purchase #5	$152.36	6.818%	$162.7479	$162.75	$162.75	$162.70
Purchase #6	$156.83	5.313%	$165.1624	$165.16	$165.15	$165.20
Purchase #7	$182.56	10.296%	$201.3564	$201.36	$201.35	$201.40
7 purchase totals =	$765.89		$829.0628	$829.06	$829.05	$829.10