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	$24.41	5.538%	$25.7618	$25.76	$25.75	$25.80
Purchase #2	$169.78	7.461%	$182.4473	$182.45	$182.45	$182.40
Purchase #3	$32.85	13.346%	$37.2342	$37.23	$37.25	$37.20
Purchase #4	$154.56	9.544%	$169.3112	$169.31	$169.30	$169.30
Purchase #5	$160.32	13.298%	$181.6394	$181.64	$181.65	$181.60
Purchase #6	$42.46	3.138%	$43.7924	$43.79	$43.80	$43.80
Purchase #7	$24.31	3.132%	$25.0714	$25.07	$25.05	$25.10
7 purchase totals =	$608.69		$665.2577	$665.25	$665.25	$665.20