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	$239.69	7.818%	$258.429	$258.43	$258.45	$258.40
Purchase #2	$45.90	9.206%	$50.1256	$50.13	$50.15	$50.10
Purchase #3	$140.29	8.795%	$152.6285	$152.63	$152.65	$152.60
Purchase #4	$146.45	5.789%	$154.928	$154.93	$154.95	$154.90
Purchase #5	$51.28	9.398%	$56.0993	$56.10	$56.10	$56.10
Purchase #6	$232.80	3.298%	$240.4777	$240.48	$240.50	$240.50
Purchase #7	$95.31	7.792%	$102.7366	$102.74	$102.75	$102.70
7 purchase totals =	$951.72		$1,015.4247	$1,015.44	$1,015.55	$1,015.30