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	$194.69	9.778%	$213.7268	$213.73	$213.75	$213.70
Purchase #2	$133.44	8.146%	$144.31	$144.31	$144.30	$144.30
Purchase #3	$16.55	10.306%	$18.2556	$18.26	$18.25	$18.30
Purchase #4	$215.85	3.705%	$223.8472	$223.85	$223.85	$223.80
Purchase #5	$88.82	3.262%	$91.7173	$91.72	$91.70	$91.70
Purchase #6	$95.87	10.386%	$105.8271	$105.83	$105.85	$105.80
Purchase #7	$43.65	6.152%	$46.3353	$46.34	$46.35	$46.30
7 purchase totals =	$788.87		$844.0193	$844.04	$844.05	$843.90