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	$210.26	11.170%	$233.746	$233.75	$233.75	$233.70
Purchase #2	$61.53	3.871%	$63.9118	$63.91	$63.90	$63.90
Purchase #3	$77.89	3.672%	$80.7501	$80.75	$80.75	$80.80
Purchase #4	$91.60	13.556%	$104.0173	$104.02	$104.00	$104.00
Purchase #5	$18.90	8.678%	$20.5401	$20.54	$20.55	$20.50
Purchase #6	$71.38	10.185%	$78.6501	$78.65	$78.65	$78.70
Purchase #7	$42.35	11.412%	$47.183	$47.18	$47.20	$47.20
7 purchase totals =	$573.91		$628.7984	$628.80	$628.80	$628.80