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	$213.94	11.678%	$238.9239	$238.92	$238.90	$238.90
Purchase #2	$72.39	12.791%	$81.6494	$81.65	$81.65	$81.60
Purchase #3	$119.48	7.565%	$128.5187	$128.52	$128.50	$128.50
Purchase #4	$170.77	6.512%	$181.8905	$181.89	$181.90	$181.90
Purchase #5	$59.51	8.380%	$64.4969	$64.50	$64.50	$64.50
Purchase #6	$142.59	9.788%	$156.5467	$156.55	$156.55	$156.50
Purchase #7	$58.39	4.300%	$60.9008	$60.90	$60.90	$60.90
7 purchase totals =	$837.07		$912.9269	$912.93	$912.90	$912.80