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	$14.59	9.386%	$15.9594	$15.96	$15.95	$16.00
Purchase #2	$125.50	13.355%	$142.2605	$142.26	$142.25	$142.30
Purchase #3	$248.83	9.834%	$273.2999	$273.30	$273.30	$273.30
Purchase #4	$18.46	11.597%	$20.6008	$20.60	$20.60	$20.60
Purchase #5	$215.61	9.738%	$236.6061	$236.61	$236.60	$236.60
Purchase #6	$175.60	12.104%	$196.8546	$196.85	$196.85	$196.90
Purchase #7	$136.46	11.684%	$152.404	$152.40	$152.40	$152.40
7 purchase totals =	$935.05		$1,037.9853	$1,037.98	$1,037.95	$1,038.10