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	$119.64	6.839%	$127.8222	$127.82	$127.80	$127.80
Purchase #2	$199.78	4.152%	$208.0749	$208.07	$208.05	$208.10
Purchase #3	$15.88	12.647%	$17.8883	$17.89	$17.90	$17.90
Purchase #4	$72.50	12.588%	$81.6263	$81.63	$81.65	$81.60
Purchase #5	$105.46	7.334%	$113.1944	$113.19	$113.20	$113.20
Purchase #6	$232.72	7.790%	$250.8489	$250.85	$250.85	$250.80
Purchase #7	$130.41	10.484%	$144.0822	$144.08	$144.10	$144.10
7 purchase totals =	$876.39		$943.5372	$943.53	$943.55	$943.50