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	$163.56	8.334%	$177.1911	$177.19	$177.20	$177.20
Purchase #2	$133.37	8.426%	$144.6078	$144.61	$144.60	$144.60
Purchase #3	$245.54	3.783%	$254.8288	$254.83	$254.85	$254.80
Purchase #4	$164.25	7.380%	$176.3717	$176.37	$176.35	$176.40
Purchase #5	$103.78	7.289%	$111.3445	$111.34	$111.35	$111.30
Purchase #6	$165.73	4.676%	$173.4795	$173.48	$173.50	$173.50
Purchase #7	$149.83	12.332%	$168.307	$168.31	$168.30	$168.30
7 purchase totals =	$1,126.06		$1,206.1304	$1,206.13	$1,206.15	$1,206.10