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	$205.75	13.398%	$233.3164	$233.32	$233.30	$233.30
Purchase #2	$168.48	10.265%	$185.7745	$185.77	$185.75	$185.80
Purchase #3	$117.75	7.541%	$126.6295	$126.63	$126.65	$126.60
Purchase #4	$170.87	5.524%	$180.3089	$180.31	$180.30	$180.30
Purchase #5	$78.54	10.647%	$86.9022	$86.90	$86.90	$86.90
Purchase #6	$164.79	8.168%	$178.25	$178.25	$178.25	$178.30
Purchase #7	$17.28	8.667%	$18.7777	$18.78	$18.80	$18.80
7 purchase totals =	$923.46		$1,009.9592	$1,009.96	$1,009.95	$1,010.00