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	$150.59	9.764%	$165.2936	$165.29	$165.30	$165.30
Purchase #2	$69.82	4.420%	$72.906	$72.91	$72.90	$72.90
Purchase #3	$50.93	8.150%	$55.0808	$55.08	$55.10	$55.10
Purchase #4	$79.30	8.185%	$85.7907	$85.79	$85.80	$85.80
Purchase #5	$167.66	6.494%	$178.5478	$178.55	$178.55	$178.50
Purchase #6	$126.28	6.189%	$134.0955	$134.10	$134.10	$134.10
Purchase #7	$72.71	12.650%	$81.9078	$81.91	$81.90	$81.90
7 purchase totals =	$717.29		$773.6222	$773.63	$773.65	$773.60