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	$128.28	10.744%	$142.0624	$142.06	$142.05	$142.10
Purchase #2	$51.98	5.820%	$55.0052	$55.01	$55.00	$55.00
Purchase #3	$226.37	13.646%	$257.2605	$257.26	$257.25	$257.30
Purchase #4	$122.84	6.391%	$130.6907	$130.69	$130.70	$130.70
Purchase #5	$177.81	5.667%	$187.8865	$187.89	$187.90	$187.90
Purchase #6	$50.94	12.796%	$57.4583	$57.46	$57.45	$57.50
Purchase #7	$99.64	5.846%	$105.465	$105.47	$105.45	$105.50
7 purchase totals =	$857.86		$935.8286	$935.84	$935.80	$936.00