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	$22.83	4.528%	$23.8637	$23.86	$23.85	$23.90
Purchase #2	$33.69	10.378%	$37.1863	$37.19	$37.20	$37.20
Purchase #3	$247.63	12.192%	$277.821	$277.82	$277.80	$277.80
Purchase #4	$117.88	11.860%	$131.8606	$131.86	$131.85	$131.90
Purchase #5	$232.45	12.450%	$261.39	$261.39	$261.40	$261.40
Purchase #6	$41.98	7.760%	$45.2376	$45.24	$45.25	$45.20
Purchase #7	$207.80	12.407%	$233.5817	$233.58	$233.60	$233.60
7 purchase totals =	$904.26		$1,010.9409	$1,010.94	$1,010.95	$1,011.00