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	$211.84	4.683%	$221.7605	$221.76	$221.75	$221.80
Purchase #2	$39.41	10.391%	$43.5051	$43.51	$43.50	$43.50
Purchase #3	$224.54	3.563%	$232.5404	$232.54	$232.55	$232.50
Purchase #4	$63.88	4.708%	$66.8875	$66.89	$66.90	$66.90
Purchase #5	$249.51	3.479%	$258.1905	$258.19	$258.20	$258.20
Purchase #6	$154.30	10.662%	$170.7515	$170.75	$170.75	$170.80
Purchase #7	$98.81	13.173%	$111.8262	$111.83	$111.85	$111.80
7 purchase totals =	$1,042.29		$1,105.4617	$1,105.47	$1,105.50	$1,105.50