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	$120.41	9.200%	$131.4877	$131.49	$131.50	$131.50
Purchase #2	$169.95	11.580%	$189.6302	$189.63	$189.65	$189.60
Purchase #3	$247.57	3.518%	$256.2795	$256.28	$256.30	$256.30
Purchase #4	$91.44	11.830%	$102.2574	$102.26	$102.25	$102.30
Purchase #5	$160.49	6.575%	$171.0422	$171.04	$171.05	$171.00
Purchase #6	$139.35	12.265%	$156.4413	$156.44	$156.45	$156.40
Purchase #7	$226.32	10.163%	$249.3209	$249.32	$249.30	$249.30
7 purchase totals =	$1,155.53		$1,256.4592	$1,256.46	$1,256.50	$1,256.40