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	$144.72	4.345%	$151.0081	$151.01	$151.00	$151.00
Purchase #2	$121.37	4.291%	$126.578	$126.58	$126.60	$126.60
Purchase #3	$173.25	12.336%	$194.6221	$194.62	$194.60	$194.60
Purchase #4	$84.36	6.425%	$89.7801	$89.78	$89.80	$89.80
Purchase #5	$133.57	12.767%	$150.6229	$150.62	$150.60	$150.60
Purchase #6	$88.79	3.159%	$91.5949	$91.59	$91.60	$91.60
Purchase #7	$36.49	9.534%	$39.969	$39.97	$39.95	$40.00
7 purchase totals =	$782.55		$844.1751	$844.17	$844.15	$844.20