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	$167.67	10.720%	$185.6442	$185.64	$185.65	$185.60
Purchase #2	$35.90	12.719%	$40.4661	$40.47	$40.45	$40.50
Purchase #3	$110.48	9.618%	$121.106	$121.11	$121.10	$121.10
Purchase #4	$168.32	13.841%	$191.6172	$191.62	$191.60	$191.60
Purchase #5	$134.59	6.367%	$143.1593	$143.16	$143.15	$143.20
Purchase #6	$101.26	6.162%	$107.4996	$107.50	$107.50	$107.50
Purchase #7	$150.47	9.552%	$164.8429	$164.84	$164.85	$164.80
7 purchase totals =	$868.69		$954.3353	$954.34	$954.30	$954.30