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	$229.90	12.651%	$258.9846	$258.98	$259.00	$259.00
Purchase #2	$20.97	4.646%	$21.9443	$21.94	$21.95	$21.90
Purchase #3	$248.45	11.441%	$276.8752	$276.88	$276.90	$276.90
Purchase #4	$162.55	4.140%	$169.2796	$169.28	$169.30	$169.30
Purchase #5	$89.89	5.716%	$95.0281	$95.03	$95.05	$95.00
Purchase #6	$212.47	7.321%	$228.0249	$228.02	$228.00	$228.00
Purchase #7	$92.89	12.422%	$104.4288	$104.43	$104.45	$104.40
7 purchase totals =	$1,057.12		$1,154.5655	$1,154.56	$1,154.65	$1,154.50