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	$72.50	13.443%	$82.2462	$82.25	$82.25	$82.20
Purchase #2	$186.25	7.259%	$199.7699	$199.77	$199.75	$199.80
Purchase #3	$133.31	8.839%	$145.0933	$145.09	$145.10	$145.10
Purchase #4	$249.74	9.339%	$273.0632	$273.06	$273.05	$273.10
Purchase #5	$62.73	9.174%	$68.4849	$68.48	$68.50	$68.50
Purchase #6	$59.89	7.630%	$64.4596	$64.46	$64.45	$64.50
Purchase #7	$118.66	7.500%	$127.5595	$127.56	$127.55	$127.60
7 purchase totals =	$883.08		$960.6766	$960.67	$960.65	$960.80