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	$185.50	3.690%	$192.345	$192.35	$192.35	$192.30
Purchase #2	$142.72	13.787%	$162.3968	$162.40	$162.40	$162.40
Purchase #3	$233.72	6.720%	$249.426	$249.43	$249.45	$249.40
Purchase #4	$27.72	7.588%	$29.8234	$29.82	$29.80	$29.80
Purchase #5	$86.82	3.775%	$90.0975	$90.10	$90.10	$90.10
Purchase #6	$182.80	7.376%	$196.2833	$196.28	$196.30	$196.30
Purchase #7	$138.66	12.348%	$155.7817	$155.78	$155.80	$155.80
7 purchase totals =	$997.94		$1,076.1537	$1,076.16	$1,076.20	$1,076.10