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	$209.43	3.626%	$217.0239	$217.02	$217.00	$217.00
Purchase #2	$62.64	7.411%	$67.2823	$67.28	$67.30	$67.30
Purchase #3	$147.77	9.273%	$161.4727	$161.47	$161.45	$161.50
Purchase #4	$139.73	7.522%	$150.2405	$150.24	$150.25	$150.20
Purchase #5	$157.55	13.320%	$178.5357	$178.54	$178.55	$178.50
Purchase #6	$49.39	10.187%	$54.4214	$54.42	$54.40	$54.40
Purchase #7	$89.54	5.374%	$94.3519	$94.35	$94.35	$94.40
7 purchase totals =	$856.05		$923.3284	$923.32	$923.30	$923.30