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	$158.77	4.240%	$165.5018	$165.50	$165.50	$165.50
Purchase #2	$217.49	9.565%	$238.2929	$238.29	$238.30	$238.30
Purchase #3	$236.88	9.458%	$259.2841	$259.28	$259.30	$259.30
Purchase #4	$19.42	5.461%	$20.4805	$20.48	$20.50	$20.50
Purchase #5	$159.35	10.243%	$175.6722	$175.67	$175.65	$175.70
Purchase #6	$195.76	11.640%	$218.5465	$218.55	$218.55	$218.50
Purchase #7	$162.93	9.650%	$178.6527	$178.65	$178.65	$178.70
7 purchase totals =	$1,150.60		$1,256.4307	$1,256.42	$1,256.45	$1,256.50