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	$177.55	12.847%	$200.3598	$200.36	$200.35	$200.40
Purchase #2	$166.59	3.648%	$172.6672	$172.67	$172.65	$172.70
Purchase #3	$75.84	3.217%	$78.2798	$78.28	$78.30	$78.30
Purchase #4	$242.45	7.288%	$260.1198	$260.12	$260.10	$260.10
Purchase #5	$180.41	11.201%	$200.6177	$200.62	$200.60	$200.60
Purchase #6	$5.47	11.234%	$6.0845	$6.08	$6.10	$6.10
Purchase #7	$58.90	9.221%	$64.3312	$64.33	$64.35	$64.30
7 purchase totals =	$907.21		$982.4600	$982.46	$982.45	$982.50