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	$231.70	12.440%	$260.5235	$260.52	$260.50	$260.50
Purchase #2	$160.69	11.696%	$179.4843	$179.48	$179.50	$179.50
Purchase #3	$44.87	12.689%	$50.5636	$50.56	$50.55	$50.60
Purchase #4	$167.70	12.744%	$189.0717	$189.07	$189.05	$189.10
Purchase #5	$51.78	8.810%	$56.3418	$56.34	$56.35	$56.30
Purchase #6	$136.52	13.706%	$155.2314	$155.23	$155.25	$155.20
Purchase #7	$158.59	6.855%	$169.4613	$169.46	$169.45	$169.50
7 purchase totals =	$951.85		$1,060.6776	$1,060.66	$1,060.65	$1,060.70