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	$46.69	10.379%	$51.536	$51.54	$51.55	$51.50
Purchase #2	$234.27	11.413%	$261.0072	$261.01	$261.00	$261.00
Purchase #3	$52.52	9.460%	$57.4884	$57.49	$57.50	$57.50
Purchase #4	$200.45	10.641%	$221.7799	$221.78	$221.80	$221.80
Purchase #5	$245.81	9.250%	$268.5474	$268.55	$268.55	$268.50
Purchase #6	$180.46	9.860%	$198.2534	$198.25	$198.25	$198.30
Purchase #7	$85.77	6.554%	$91.3914	$91.39	$91.40	$91.40
7 purchase totals =	$1,045.97		$1,150.0037	$1,150.01	$1,150.05	$1,150.00