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	$131.67	8.304%	$142.6039	$142.60	$142.60	$142.60
Purchase #2	$113.30	7.657%	$121.9754	$121.98	$122.00	$122.00
Purchase #3	$197.69	12.334%	$222.0731	$222.07	$222.05	$222.10
Purchase #4	$106.48	4.780%	$111.5697	$111.57	$111.55	$111.60
Purchase #5	$230.55	4.319%	$240.5075	$240.51	$240.50	$240.50
Purchase #6	$82.74	10.805%	$91.6801	$91.68	$91.70	$91.70
Purchase #7	$147.51	6.477%	$157.0642	$157.06	$157.05	$157.10
7 purchase totals =	$1,009.94		$1,087.4739	$1,087.47	$1,087.45	$1,087.60