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	$40.59	6.528%	$43.2397	$43.24	$43.25	$43.20
Purchase #2	$162.39	11.496%	$181.0584	$181.06	$181.05	$181.10
Purchase #3	$201.78	10.478%	$222.9225	$222.92	$222.90	$222.90
Purchase #4	$66.51	7.447%	$71.463	$71.46	$71.45	$71.50
Purchase #5	$228.56	12.455%	$257.0271	$257.03	$257.05	$257.00
Purchase #6	$227.67	10.227%	$250.9538	$250.95	$250.95	$251.00
Purchase #7	$97.51	7.545%	$104.8671	$104.87	$104.85	$104.90
7 purchase totals =	$1,025.01		$1,131.5316	$1,131.53	$1,131.50	$1,131.60