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	$50.42	7.296%	$54.0986	$54.10	$54.10	$54.10
Purchase #2	$238.52	10.795%	$264.2682	$264.27	$264.25	$264.30
Purchase #3	$140.44	3.600%	$145.4958	$145.50	$145.50	$145.50
Purchase #4	$76.83	4.518%	$80.3012	$80.30	$80.30	$80.30
Purchase #5	$178.71	9.664%	$195.9805	$195.98	$196.00	$196.00
Purchase #6	$182.95	12.213%	$205.2937	$205.29	$205.30	$205.30
Purchase #7	$13.86	6.692%	$14.7875	$14.79	$14.80	$14.80
7 purchase totals =	$881.73		$960.2255	$960.23	$960.25	$960.30