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	$184.30	11.141%	$204.8329	$204.83	$204.85	$204.80
Purchase #2	$163.47	3.542%	$169.2601	$169.26	$169.25	$169.30
Purchase #3	$95.96	4.217%	$100.0066	$100.01	$100.00	$100.00
Purchase #4	$250.91	7.477%	$269.6705	$269.67	$269.65	$269.70
Purchase #5	$165.51	4.821%	$173.4892	$173.49	$173.50	$173.50
Purchase #6	$53.63	3.291%	$55.395	$55.40	$55.40	$55.40
Purchase #7	$72.62	7.570%	$78.1173	$78.12	$78.10	$78.10
7 purchase totals =	$986.40		$1,050.7716	$1,050.78	$1,050.75	$1,050.80