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	$94.79	6.306%	$100.7675	$100.77	$100.75	$100.80
Purchase #2	$176.53	3.453%	$182.6256	$182.63	$182.65	$182.60
Purchase #3	$101.78	11.403%	$113.386	$113.39	$113.40	$113.40
Purchase #4	$226.54	10.495%	$250.3154	$250.32	$250.30	$250.30
Purchase #5	$183.31	7.429%	$196.9281	$196.93	$196.95	$196.90
Purchase #6	$61.57	7.832%	$66.3922	$66.39	$66.40	$66.40
Purchase #7	$104.38	7.490%	$112.1981	$112.20	$112.20	$112.20
7 purchase totals =	$948.90		$1,022.6129	$1,022.63	$1,022.65	$1,022.60