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	$173.71	13.104%	$196.473	$196.47	$196.45	$196.50
Purchase #2	$60.49	6.608%	$64.4872	$64.49	$64.50	$64.50
Purchase #3	$49.38	13.614%	$56.1026	$56.10	$56.10	$56.10
Purchase #4	$137.95	3.444%	$142.701	$142.70	$142.70	$142.70
Purchase #5	$32.56	7.592%	$35.032	$35.03	$35.05	$35.00
Purchase #6	$19.96	13.387%	$22.632	$22.63	$22.65	$22.60
Purchase #7	$85.85	3.535%	$88.8848	$88.88	$88.90	$88.90
7 purchase totals =	$559.90		$606.3126	$606.30	$606.35	$606.30