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	$163.31	3.379%	$168.8282	$168.83	$168.85	$168.80
Purchase #2	$154.92	10.473%	$171.1448	$171.14	$171.15	$171.10
Purchase #3	$223.73	10.785%	$247.8593	$247.86	$247.85	$247.90
Purchase #4	$132.81	9.750%	$145.759	$145.76	$145.75	$145.80
Purchase #5	$32.31	9.228%	$35.2916	$35.29	$35.30	$35.30
Purchase #6	$123.52	10.667%	$136.6959	$136.70	$136.70	$136.70
Purchase #7	$71.49	10.210%	$78.7891	$78.79	$78.80	$78.80
7 purchase totals =	$902.09		$984.3679	$984.37	$984.40	$984.40