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	$48.76	13.545%	$55.3645	$55.36	$55.35	$55.40
Purchase #2	$68.59	5.277%	$72.2095	$72.21	$72.20	$72.20
Purchase #3	$31.37	12.247%	$35.2119	$35.21	$35.20	$35.20
Purchase #4	$148.32	12.234%	$166.4655	$166.47	$166.45	$166.50
Purchase #5	$249.72	12.802%	$281.6892	$281.69	$281.70	$281.70
Purchase #6	$80.85	3.822%	$83.9401	$83.94	$83.95	$83.90
Purchase #7	$221.65	12.133%	$248.5428	$248.54	$248.55	$248.50
7 purchase totals =	$849.26		$943.4235	$943.42	$943.40	$943.40