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	$250.63	13.426%	$284.2796	$284.28	$284.30	$284.30
Purchase #2	$33.55	3.721%	$34.7984	$34.80	$34.80	$34.80
Purchase #3	$73.38	12.492%	$82.5466	$82.55	$82.55	$82.50
Purchase #4	$98.48	3.530%	$101.9563	$101.96	$101.95	$102.00
Purchase #5	$181.47	9.689%	$199.0526	$199.05	$199.05	$199.10
Purchase #6	$156.40	9.863%	$171.8257	$171.83	$171.85	$171.80
Purchase #7	$153.51	7.497%	$165.0186	$165.02	$165.00	$165.00
7 purchase totals =	$947.42		$1,039.4778	$1,039.49	$1,039.50	$1,039.50