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	$142.77	5.340%	$150.3939	$150.39	$150.40	$150.40
Purchase #2	$29.84	12.709%	$33.6324	$33.63	$33.65	$33.60
Purchase #3	$80.31	10.546%	$88.7795	$88.78	$88.80	$88.80
Purchase #4	$95.40	10.139%	$105.0726	$105.07	$105.05	$105.10
Purchase #5	$179.54	11.404%	$200.0147	$200.01	$200.00	$200.00
Purchase #6	$34.30	9.814%	$37.6662	$37.67	$37.65	$37.70
Purchase #7	$162.35	12.294%	$182.3093	$182.31	$182.30	$182.30
7 purchase totals =	$724.51		$797.8686	$797.86	$797.85	$797.90