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	$111.42	12.694%	$125.5637	$125.56	$125.55	$125.60
Purchase #2	$152.25	8.558%	$165.2796	$165.28	$165.30	$165.30
Purchase #3	$146.25	9.247%	$159.7737	$159.77	$159.75	$159.80
Purchase #4	$185.52	8.252%	$200.8291	$200.83	$200.85	$200.80
Purchase #5	$104.47	8.466%	$113.3144	$113.31	$113.30	$113.30
Purchase #6	$198.75	9.374%	$217.3808	$217.38	$217.40	$217.40
Purchase #7	$148.64	5.433%	$156.7156	$156.72	$156.70	$156.70
7 purchase totals =	$1,047.30		$1,138.8569	$1,138.85	$1,138.85	$1,138.90