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	$43.67	11.495%	$48.6899	$48.69	$48.70	$48.70
Purchase #2	$142.38	6.608%	$151.7885	$151.79	$151.80	$151.80
Purchase #3	$244.78	10.113%	$269.5346	$269.53	$269.55	$269.50
Purchase #4	$63.44	13.110%	$71.757	$71.76	$71.75	$71.80
Purchase #5	$142.73	9.521%	$156.3193	$156.32	$156.30	$156.30
Purchase #6	$117.83	11.660%	$131.569	$131.57	$131.55	$131.60
Purchase #7	$74.77	10.409%	$82.5528	$82.55	$82.55	$82.60
7 purchase totals =	$829.60		$912.2111	$912.21	$912.20	$912.30