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	$41.65	9.468%	$45.5934	$45.59	$45.60	$45.60
Purchase #2	$176.44	13.767%	$200.7305	$200.73	$200.75	$200.70
Purchase #3	$164.89	10.637%	$182.4293	$182.43	$182.45	$182.40
Purchase #4	$106.69	8.152%	$115.3874	$115.39	$115.40	$115.40
Purchase #5	$195.60	13.564%	$222.1312	$222.13	$222.15	$222.10
Purchase #6	$189.91	5.365%	$200.0987	$200.10	$200.10	$200.10
Purchase #7	$153.99	9.514%	$168.6406	$168.64	$168.65	$168.60
7 purchase totals =	$1,029.17		$1,135.0111	$1,135.01	$1,135.10	$1,134.90