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	$194.91	13.183%	$220.605	$220.61	$220.60	$220.60
Purchase #2	$28.56	3.740%	$29.6281	$29.63	$29.65	$29.60
Purchase #3	$56.29	13.216%	$63.7293	$63.73	$63.75	$63.70
Purchase #4	$110.25	3.275%	$113.8607	$113.86	$113.85	$113.90
Purchase #5	$94.69	9.647%	$103.8247	$103.82	$103.80	$103.80
Purchase #6	$126.89	9.759%	$139.2732	$139.27	$139.25	$139.30
Purchase #7	$249.89	9.254%	$273.0148	$273.01	$273.00	$273.00
7 purchase totals =	$861.48		$943.9358	$943.93	$943.90	$943.90