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	$163.39	11.512%	$182.1995	$182.20	$182.20	$182.20
Purchase #2	$66.49	9.143%	$72.5692	$72.57	$72.55	$72.60
Purchase #3	$122.53	3.508%	$126.8284	$126.83	$126.85	$126.80
Purchase #4	$137.57	3.518%	$142.4097	$142.41	$142.40	$142.40
Purchase #5	$157.30	3.283%	$162.4642	$162.46	$162.45	$162.50
Purchase #6	$171.28	5.683%	$181.0138	$181.01	$181.00	$181.00
Purchase #7	$192.54	13.874%	$219.253	$219.25	$219.25	$219.30
7 purchase totals =	$1,011.10		$1,086.7378	$1,086.73	$1,086.70	$1,086.80