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	$158.84	8.557%	$172.4319	$172.43	$172.45	$172.40
Purchase #2	$158.81	6.670%	$169.4026	$169.40	$169.40	$169.40
Purchase #3	$86.26	5.113%	$90.6705	$90.67	$90.65	$90.70
Purchase #4	$202.89	7.413%	$217.9302	$217.93	$217.95	$217.90
Purchase #5	$143.50	8.838%	$156.1825	$156.18	$156.20	$156.20
Purchase #6	$53.53	3.459%	$55.3816	$55.38	$55.40	$55.40
Purchase #7	$180.38	8.565%	$195.8295	$195.83	$195.85	$195.80
7 purchase totals =	$984.21		$1,057.8288	$1,057.82	$1,057.90	$1,057.80