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	$212.89	10.353%	$234.9305	$234.93	$234.95	$234.90
Purchase #2	$54.54	11.647%	$60.8923	$60.89	$60.90	$60.90
Purchase #3	$180.46	11.180%	$200.6354	$200.64	$200.65	$200.60
Purchase #4	$250.74	9.232%	$273.8883	$273.89	$273.90	$273.90
Purchase #5	$205.74	12.216%	$230.8732	$230.87	$230.85	$230.90
Purchase #6	$72.70	10.730%	$80.5007	$80.50	$80.50	$80.50
Purchase #7	$32.84	10.513%	$36.2925	$36.29	$36.30	$36.30
7 purchase totals =	$1,009.91		$1,118.0129	$1,118.01	$1,118.05	$1,118.00