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	$133.36	13.120%	$150.8568	$150.86	$150.85	$150.90
Purchase #2	$227.77	13.718%	$259.0155	$259.02	$259.00	$259.00
Purchase #3	$94.64	5.439%	$99.7875	$99.79	$99.80	$99.80
Purchase #4	$148.72	4.224%	$155.0019	$155.00	$155.00	$155.00
Purchase #5	$58.52	4.568%	$61.1932	$61.19	$61.20	$61.20
Purchase #6	$206.64	7.177%	$221.4706	$221.47	$221.45	$221.50
Purchase #7	$121.72	7.208%	$130.4936	$130.49	$130.50	$130.50
7 purchase totals =	$991.37		$1,077.8191	$1,077.82	$1,077.80	$1,077.90