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	$218.80	7.552%	$235.3238	$235.32	$235.30	$235.30
Purchase #2	$47.56	4.686%	$49.7887	$49.79	$49.80	$49.80
Purchase #3	$190.42	13.684%	$216.4771	$216.48	$216.50	$216.50
Purchase #4	$196.55	11.812%	$219.7665	$219.77	$219.75	$219.80
Purchase #5	$17.51	4.795%	$18.3496	$18.35	$18.35	$18.30
Purchase #6	$71.30	3.646%	$73.8996	$73.90	$73.90	$73.90
Purchase #7	$152.76	7.758%	$164.6111	$164.61	$164.60	$164.60
7 purchase totals =	$894.90		$978.2164	$978.22	$978.20	$978.20