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	$122.71	3.597%	$127.1239	$127.12	$127.10	$127.10
Purchase #2	$112.52	13.426%	$127.6269	$127.63	$127.65	$127.60
Purchase #3	$101.50	13.821%	$115.5283	$115.53	$115.55	$115.50
Purchase #4	$205.75	12.870%	$232.23	$232.23	$232.25	$232.20
Purchase #5	$11.25	9.204%	$12.2855	$12.29	$12.30	$12.30
Purchase #6	$104.82	4.735%	$109.7832	$109.78	$109.80	$109.80
Purchase #7	$42.63	4.222%	$44.4298	$44.43	$44.45	$44.40
7 purchase totals =	$701.18		$769.0076	$769.01	$769.10	$768.90