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	$78.56	10.619%	$86.9023	$86.90	$86.90	$86.90
Purchase #2	$138.64	3.811%	$143.9236	$143.92	$143.90	$143.90
Purchase #3	$95.38	4.838%	$99.9945	$99.99	$100.00	$100.00
Purchase #4	$119.40	5.745%	$126.2595	$126.26	$126.25	$126.30
Purchase #5	$234.89	3.583%	$243.3061	$243.31	$243.30	$243.30
Purchase #6	$246.27	13.222%	$278.8318	$278.83	$278.85	$278.80
Purchase #7	$40.75	7.580%	$43.8389	$43.84	$43.85	$43.80
7 purchase totals =	$953.89		$1,023.0567	$1,023.05	$1,023.05	$1,023.00