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	$171.81	5.581%	$181.3987	$181.40	$181.40	$181.40
Purchase #2	$17.77	9.424%	$19.4446	$19.44	$19.45	$19.40
Purchase #3	$161.26	4.505%	$168.5248	$168.52	$168.50	$168.50
Purchase #4	$185.37	7.715%	$199.6713	$199.67	$199.65	$199.70
Purchase #5	$25.87	5.264%	$27.2318	$27.23	$27.25	$27.20
Purchase #6	$243.52	4.870%	$255.3794	$255.38	$255.40	$255.40
Purchase #7	$182.72	9.865%	$200.7453	$200.75	$200.75	$200.70
7 purchase totals =	$988.32		$1,052.3959	$1,052.39	$1,052.40	$1,052.30