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	$50.73	10.578%	$56.0962	$56.10	$56.10	$56.10
Purchase #2	$162.40	9.533%	$177.8816	$177.88	$177.90	$177.90
Purchase #3	$128.93	10.201%	$142.0821	$142.08	$142.10	$142.10
Purchase #4	$152.28	7.873%	$164.269	$164.27	$164.25	$164.30
Purchase #5	$216.47	11.156%	$240.6194	$240.62	$240.60	$240.60
Purchase #6	$160.32	12.439%	$180.2622	$180.26	$180.25	$180.30
Purchase #7	$151.55	10.423%	$167.3461	$167.35	$167.35	$167.30
7 purchase totals =	$1,022.68		$1,128.5566	$1,128.56	$1,128.55	$1,128.60