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	$35.66	7.542%	$38.3495	$38.35	$38.35	$38.30
Purchase #2	$31.95	12.316%	$35.885	$35.89	$35.90	$35.90
Purchase #3	$69.25	13.588%	$78.6597	$78.66	$78.65	$78.70
Purchase #4	$89.86	5.832%	$95.1006	$95.10	$95.10	$95.10
Purchase #5	$226.31	12.546%	$254.7029	$254.70	$254.70	$254.70
Purchase #6	$192.51	4.311%	$200.8091	$200.81	$200.80	$200.80
Purchase #7	$199.56	8.869%	$217.259	$217.26	$217.25	$217.30
7 purchase totals =	$845.10		$920.7658	$920.77	$920.75	$920.80