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	$231.79	10.465%	$256.0468	$256.05	$256.05	$256.00
Purchase #2	$37.86	6.809%	$40.4379	$40.44	$40.45	$40.40
Purchase #3	$116.99	10.811%	$129.6378	$129.64	$129.65	$129.60
Purchase #4	$81.63	9.619%	$89.482	$89.48	$89.50	$89.50
Purchase #5	$233.31	4.118%	$242.9177	$242.92	$242.90	$242.90
Purchase #6	$226.66	8.271%	$245.407	$245.41	$245.40	$245.40
Purchase #7	$72.84	7.166%	$78.0597	$78.06	$78.05	$78.10
7 purchase totals =	$1,001.08		$1,081.9889	$1,082.00	$1,082.00	$1,081.90